Cells genetically modified to comprise pancreatic islet glucokinase and uses thereof

ABSTRACT

The present invention relates generally to a population of cells genetically modified to produce insulin in a glucose responsive manner and uses thereof. More particularly, the present invention relates to a population of cells genetically modified to produce insulin in response to physiologically relevant levels of glucose and uses thereof. The cells of the present invention are useful in a wide variety of applications, in particular in the context of therapeutic and prophylactic regimes directed to the treatment of diabetes and/or the amelioration of symptoms associated with diabetes, based on the transplantation of the cells of the present invention into mammals requiring treatment. Also facilitated is the design of in vitro based screening systems for testing the therapeutic effectiveness and/or toxicity of potential adjunctive treatment regimes.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.15/652,000, filed Jul. 17, 2017, which is a continuation of U.S.application Ser. No. 15/053,992, filed Feb. 25, 2016, issued as U.S.Pat. No. 9,732,329 on Aug. 15, 2017, which is a continuation of U.S.application Ser. No. 14/185,716, filed Feb. 20, 2014, issued as U.S.Pat. No. 9,365,829 on Jun. 14, 2016, which is a continuation of U.S.application Ser. No. 12/672,832, filed on Jun. 3, 2011, now abandoned,and which claims the benefit of priority to and is a U.S. National PhaseApplication of PCT International Application Number PCT/AU2008/001160,filed on Aug. 8, 2008, designating the United States of America andpublished in the English language, which is an International Applicationof and claims the benefit of priority to Australian Patent ApplicationNo. 2007904310, filed on Aug. 10, 2007. The disclosures of theabove-referenced applications are hereby expressly incorporated byreference in their entireties.

REFERENCE TO SEQUENCE LISTING

The present application is being filed along with a sequence listing inelectronic format. The sequence listing is provided as a file entitledSequenceListing-WMRK7-001C4, created Aug. 4, 2020 which is 26 kB insize. The information in the electronic format of the sequence listingis incorporated herein by reference in its entirety.

FIELD OF THE INVENTION

The present invention relates generally to a population of cellsgenetically modified to produce insulin in a glucose responsive mannerand uses thereof. More particularly, the present invention relates to apopulation of cells genetically modified to produce insulin in responseto physiologically relevant levels of glucose and uses thereof. Thecells of the present invention are useful in a wide variety ofapplications, in particular in the context of therapeutic andprophylactic regimes directed to the treatment of diabetes and/or theamelioration of symptoms associated with diabetes, based on thetransplantation of the cells of the present invention into mammalsrequiring treatment. Also facilitated is the design of in vitro basedscreening systems for testing the therapeutic effectiveness and/ortoxicity of potential adjunctive treatment regimes.

BACKGROUND OF THE INVENTION

Bibliographic details of the publications referred to by author in thisspecification are collected alphabetically at the end of thedescription.

The reference to any prior art in this specification is not, and shouldnot be taken as, an acknowledgment or any form of suggestion that thatprior art forms part of the common general knowledge in Australia.

Diabetes mellitus is characterised by an abnormality of carbohydratemetabolism resulting in elevated glucose levels in both the blood andthe urine. The failure of the human body to properly metabolise theglucose is caused by defects in insulin secretion or use of insulin.Insulin is produced by β-cells in the islets of the pancreas and permitsthe body to utilise glucose as a source of energy. When this processcannot occur, the body compensates by utilising alternative sources ofenergy such as stored fats. However, this leads to rapidly rising levelsof glucose and the accumulation of ketones in the bloodstream due to theoccurrence of extensive fat metabolism.

Diabetes is broadly classified into two groups termed Type 1 diabetesand Type 2 diabetes. Type 1 diabetes (often referred to as juvenileonset diabetes due to its appearance in childhood or early adolescence)is a debilitating autoimmune condition caused by the selectivedestruction of insulin producing β-cells in the islets of the pancreas.Its onset is abrupt and occurs typically prior to the age of 20 years.Presently, however, Type 1 diabetes is increasingly presenting inadults. This disease is characterised by lack of β-cell function and noinsulin production, and therefore insulin therapy is required. Type 2diabetes, however, is characterised by insulin resistance, a conditionin which the body fails to properly use insulin, which is oftenaccompanied by obesity and other metabolic disorders. There arefrequently no overt symptoms observed. Insulin secretory defects areevident very early in disease in both Type 1 and Type 2 diabetes,despite their differing aetiology.

In the absence of treatment, diabetes can be fatal while poorlycontrolled diabetes leads to the appearance of complications such asdiabetic glomerulosclerosis, wherein the kidneys are irreversiblydamaged leading to renal failure. Treatment of type 1 diabetes and alsosevere symptoms of type 2 diabetes is generally by daily insulininjection to replace the insulin which the damaged β cells are no longerable to produce. However, even in the face of an optimised treatmentregime of this type, complications and side effects are common. Forexample, diabetic vascular complications, affecting both micro- andmacro-blood vessels, represent major causes of disability and death inthe patients with type 1 and type 2 diabetes. In fact, diabetes is nowrecognized as a potent and independent risk factor for the developmentof coronary, cerebrovascular and peripheral atherosclerotic disease(Beckman et al., 2002, JAMA 287:2570-2581).

Treatment of diabetes can also be effected via the transplantation ofinsulin-secreting tissue. However, since this latter strategy relies onthe use of scarce human tissue as a source, it seems unlikely that therewill ever be sufficient numbers of organs available to assist more thana selected number of insulin-dependent diabetics. Furthermore, thesepatients would have to undergo a long term regimen of immunosuppressivedrugs.

Accordingly, there is an ongoing need to develop alternative and moreeffective methods of regulating glucose levels in diabetic patients. Inwork leading up to the present invention, a population of cells havebeen generated which synthesise, store and secrete insulin in responseto glucose stimulation. However, whereas existing cell lines of thistype have secreted insulin in a highly sensitive manner, and thereforein response to even very low glucose levels, the genetic modificationintroduced into the cells of the present invention has refined theirglucose responsiveness such that insulin is produced only in response tophysiologically relevant levels of glucose, that is, levels equal to orgreater than the minimum levels of glucose which would result inpancreatic β cell insulin production in normal individuals.

SUMMARY OF THE INVENTION

Throughout this specification and the claims which follow, unless thecontext requires otherwise, the word “comprise”, and variations such as“comprises” and “comprising”, will be understood to imply the inclusionof a stated integer or step or group of integers or steps but not theexclusion of any other integer or step or group of integers or steps.

As used herein, the term “derived from” shall be taken to indicate thata particular integer or group of integers has originated from thespecies specified, but has not necessarily been obtained directly fromthe specified source. Further, as used herein the singular forms of “a”,“and” and “the” include plural referents unless the context clearlydictates otherwise.

The subject specification contains nucleotide sequence informationprepared using the programme PatentIn Version 3.1, presented hereinafter the bibliography. Each nucleotide sequence is identified in thesequence listing by the numeric indicator <210> followed by the sequenceidentifier (eg. <210>1, <210>2, etc). The length, type of sequence (DNA,etc) and source organism for each nucleotide sequence is indicated byinformation provided in the numeric indicator fields <211>, <212> and<213>, respectively. Nucleotide sequences referred to in thespecification are identified by the indicator SEQ ID NO: followed by thesequence identifier (eg. SEQ ID NO:1, SEQ ID NO:2, etc.). The sequenceidentifier referred to in the specification correlates to theinformation provided in numeric indicator field <400> in the sequencelisting, which is followed by the sequence identifier (eg. <400>1,<400>2, etc). That is SEQ ID NO:1 as detailed in the specificationcorrelates to the sequence indicated as <400>1 in the sequence listing.

One aspect of the present invention is directed to a geneticallymodified mammalian cell, which cell is capable of secreting insulin,said genetic modification comprising the transfection of said cell witha nucleic acid molecule encoding pancreatic islet glucokinase.

In another aspect there is provided a genetically modified mammalianhepatocyte, which hepatocyte is capable of secreting insulin, saidgenetic modification comprising the transfection of said hepatocyte witha nucleic acid molecule encoding pancreatic islet glucokinase.

Yet another aspect of the present invention is directed to a geneticallymodified mammalian hepatocyte, which hepatocyte is capable of secretinginsulin, said genetic modification comprising the transfection of saidhepatocyte with a nucleic acid molecule encoding pancreatic isletglucokinase and wherein said cell is responsive to glucose in aphysiologically relevant manner.

Still another aspect of the present invention provides a geneticallymodified human hepatocyte, which hepatocyte is capable of secretinginsulin, said genetic modification comprising the transfection of saidhepatocyte with a nucleic acid molecule encoding pancreatic isletglucokinase.

Yet still another aspect of the present invention provides a geneticallymodified human hepatocyte, which hepatocyte is capable of secretinginsulin, said genetic modification comprising the transfection of saidcell with a vector, which vector comprises a nucleic acid moleculeencoding pancreatic islet glucokinase.

Still yet another aspect of the present invention provides a geneticallymodified Huh7ins cell, said genetic modification comprising thetransfection of said Huh7ins cell with a vector, which vector comprisesa nucleic acid molecule encoding pancreatic islet glucokinase.

A further aspect of the present invention is directed to a method oftherapeutically and/or prophylactically treating a condition in amammal, which condition is characterised by the aberrant production offunctional insulin, said method comprising introducing into said mammalan effective number of the genetically modified cells hereinbeforedefined.

Another further aspect of the present invention provides a method oftherapeutically and/or prophylactically treating diabetes in a mammal,said method comprising introducing into said mammal an effective numberof the genetically modified cells hereinbefore defined.

Still another aspect of the present invention contemplates a method ofmodulating insulin levels in a mammal said method comprising introducinginto said subject an effective number of the genetically modified cellshereinbefore defined.

Yet another aspect of the present invention contemplates a method ofmodulating glucose levels in a mammal said method comprising introducinginto said subject an effective number of the genetically modified cellshereinbefore defined.

Still another aspect of the present invention is directed to the use ofgenetically modified cells hereinbefore defined in the manufacture of amedicament for the treatment of a condition in a mammal, which conditionis characterised by the aberrant production of functional insulin.

According to yet another aspect of the present invention, there isprovided a method of assessing the effect of a treatment or cultureregime on the phenotypic state of the genetically modified cells ashereinbefore defined, said method comprising subjecting said cells tosaid treatment regime and screening for an altered phenotypic state.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic representation of pIRESpuro3. The human isletglucokinase cDNA was cut out of the vector pBluescriptSK at the E_(COR)I site and subsequently cloned into the EcoRI site of the multi-cloningsite of the pIRESpuro3 vectors.

FIGS. 2A-2C show a schematic representation of the pIERSpuro3 vectorsequence of the pIERSpuro3 vector (5157 base pairs sequence SEQ ID NO:1)with insert human islet glucokinase cDNA (2733 base pairs SEQ ID NO:2)highlighted in enlarged text. The nucleotides in bold text represent theremnant nucleotides of the pBluescriptSK cloning vector. SEQ ID NO:3represents the vector sequence incorporating the islet glucokinase cDNAsequence.

FIG. 3 is an image of the RT/PCR expression of human islet glucokinase,220 bp product. DNA marker (lane 1), Melligen cells clone 6 (lane 2),Huh7ins cells with pIRISpuro3 vector only (lane 3), Huh7ins cells (lane4).

FIG. 4 is an image of a Western blot analysis for human glucokinase inHuh7ins (lane 1), Huh7ins cells with pIRISpuro3 vector only (lane 2),Melligen cells (lane 3).

FIG. 5 is a graphical representation of Glucokinase activity of (1)Huh7, (2) Huh7ins, (3) Huh7ins (empty vector) and (4) Melligen cells inthe presence of 20 mM glucose (FIG. 5A), and 20 mM glucose plus 10 mMglucose-6-phosphate (FIG. 5B). Means±SEM, n=6.

FIG. 6 is a graphical representation of insulin secretion from Huh7ins(FIG. 6A) and Melligen (FIG. 6B) cells in response to increasingconcentrations of glucose: 1.5-20 mM. Values are expressed as means±S.E. (n=3).

FIG. 7 is a graphical representation of insulin secretion from Melligencells in response to increasing concentrations of glucose: 3.75-5.0 mM.Values are expressed as means±S. E. (n=6).

FIG. 8 shows a transmission electron micrograph of Melligen cellsshowing secretory vesicles with dense granules (sg) surrounded by a palehalo (bar=1 μM;

FIG. 8A); and an immuno-electron micrograph showing localization ofinsulin in Melligen cells (bar=460 nm; FIG. 8B).

FIG. 9 is a graphical representation of MIN-6 cells incubated with thepro-inflammatory cytokines IFN-γ (384 ng/mL), TNF-α (long/mL) and IL-1β(2000 pg/mL) in combination and individually over 6 days replacing thecytokines and media once every 2 days (FIG. 9A) and over 8 days with thecytokines and media changed daily (FIG. 9B). Control cells wereincubated in media alone. Results expressed as mean±SE (n=4; SEs fellwithin data points).

FIG. 10 is graphical representations of the treatment of MIN-6 cellswith cytokine concentrations titrated over 8 days at twice (IFN-γ (768ng/mL), TNF-α (20 ng/mL) and IL-1β (4000 pg/mL)) (FIG. 10A) and at half(IFN-γ (192 ng/mL), TNF-α (5 ng/mL) and IL-1β (1000 pg/mL)) the initialconcentrations used (FIG. 10B). Results expressed as mean±SE (n=4; SEsfell within data points).

FIG. 11 is a graphical representation of the growth kinetics of MIN 6cells and the three liver cell lines used. Cells were initially seededat a density of 1×10⁴ cells/mL, for liver cell lines, and 2×10⁴cells/mL, for MIN-6 cells, into six well plates. Cell counts wereobtained using a haemocytometer every second day throughout the periodstudied, FIG. 11A shows results with MIN-6 cells, FIG. 11B shows resultswith Huh7 cells, FIG. 11C shows results with Huh7ins cells, and FIG. 11Dshows results with Melligen cells. Results expressed as mean±SE, (n=3)(At some time points the SEs fall within the data point).

FIG. 12 is a graphical representation of an MTT viability assay onHuh7ins cells performed to ensure that exponential growth was detectedby the assay over 8 days. Results are expressed as mean±SE (n=6; SEsfell within data points).

FIG. 13 is a graphical representation of an MTT viability assay on MIN-6cells incubated with the cytokines IFN-γ (384 ng/mL), TNF-α (long/mL)and IL-1β (2000 pg/mL). Media was changed daily. Cell viability wasdetermined at various time points throughout the 10-day period. Cytokineconcentrations used were 1 times more than (FIG. 13A), 2 times more than(FIG. 13B), and 5 times more than (FIG. 13C) the initial concentrations.Results expressed as mean±SE (n=4; SEs fell within data points).

FIG. 14 is a graphical representation of an MTT viability assay on MIN-6cells (FIG. 14A), Huh7 cells (FIG. 14B), Huh7ins (FIG. 14C), andMelligen cells (FIG. 14D) incubated with the cytokines IFN-γ (384ng/mL), TNF-α (10 ng/mL) and IL-10 (2000 pg/mL). Cytokines were changeddaily over a 10-day period. Results expressed as mean±SE (n=5) (At sometime points the SEs fall within the data point *P<0.01, **P<0.001).

FIG. 15 shows images of Annexin/PI staining of Huh7ins at both 24 h and48 h which shows no early or late apoptotic cell death. Only a necroticpopulation was detected and the difference between control and treatedcells was not significant p>0.05. These panels are representative offour independent experiments. FIG. 15A and FIG. 15B show control cellsat 24 h and 48 h respectively, whereas FIG. 15C and FIG. 15D showcytokine treated cells at 24 h and 48 h, respectively.

FIG. 16 are images showing that at both 24 h and 48 h Melligen cellsshowed no early or late apoptotic cell death. Only a necrotic populationwas detected and the difference between control and treated cells wasnot significant p>0.05. These panels are representative of fourindependent experiments. FIG. 16A and FIG. 16B show control cells at 24h and 48 h respectively, whereas FIG. 16C and FIG. 16D show cytokinetreated cells at 24 h and 48 h, respectively.

FIG. 17 shows images of Huh7ins PI only staining showing that there wasno sub-G1 peak evident in treated and control cells at 24 h and 48 h.These panels are representative of four independent experiments. FIG.17A and FIG. 17B show control cells at 24 h and 48 h respectively,whereas FIG. 17C and FIG. 17D show cytokine treated cells at 24 h and 48h, respectively.

FIG. 18 shows images of Melligen cells PI only staining showing thatthere was no sub-G1 peak evident in treated and control cells at 24 hand 48 h. These panels are representative of four independentexperiments. FIG. 18A and FIG. 18B show control cells at 24 h and 48 hrespectively, whereas FIG. 18C and FIG. 18D show cytokine treated cellsat 24 h and 48 h, respectively.

FIG. 19 shows images of the cell morphology of untreated MIN-6 cellsfollowing 1 day (FIG. 19A), 6 days (FIG. 19B), and 12 days (FIG. 19C) ofincubation without cytokines. The cell morphology of MIN-6 cellsfollowing cytokine treatment with IFN-γ, TNF-α and IL-1β can be seen in1 day (FIG. 19D), 6 days (FIG. 19E), and 12 days (FIG. 19F). (100×magnification).

FIG. 20 shows images of the cell morphology of untreated Huh7ins cellsfollowing 1 day (FIG. 20A), 6 days (FIG. 20B), and 12 days (FIG. 20C).The cell morphology of Huh7ins cells incubated with the cytokines IFN-γ,TNF-α and IL-1β following the same time points 1 day (FIG. 20D), 6 days(FIG. 20E), and 12 days (FIG. 20F). (100× magnification). Morphology ofthe Melligen cells was the same as the Huh7ins cells.

FIG. 21 is an image showing RT-PCR performed using primers for IFNR1,IFNR2, IL1R1, IL1R2, TNFR1 and TNFR2 cytokine receptors. Lanes containcDNA for: 1-Pancreatic Islet Cells (positive control) 2-Huh7 Cells3-Huh7ins Cells 4-TAO Cells 5-Negative control. Results show bands forIFNR1, IFNR2, IL1R1, IL1R2 and TNFR1 but not TNFR2 cytokine receptor.The TNFR2 Cytokine Receptor was not detected at the Molecular Level inthe liver cell lines.

FIG. 22 is an image of RT-PCR performed using primers for IκBα, IκBβ andIκBε. Lanes contain cDNA for: control and treated pancreatic islet cells(positive control), control and treated Huh7 Cells, control and treatedHuh7ins Cells, and control and treated Melligen Cells. Results showbands for IκBα, IκBβ, IκBε and iNOS but not MCP-1.

FIG. 23 is a graphical representation of real time PCR results showingthat inhibitors of NFκB are down-regulated in the Melligen cells.Down-stream effector molecule, Fas, is also down-regulated. These trendsin gene expression were also seen in Huh7 and Huh7ins cells.

FIG. 24 shows a graphical representation showing NO concentrations inMin 6 (FIG. 24A), Huh7 (FIG. 24B), Huh7ins (FIG. 24C), and Melligen(FIG. 24D) cells. Increased NO concentrations were not detected in livercell lines after 48 h cytokine treatment, using the modified Greissreaction. Results are expressed as mean±SE (n=6).

FIG. 25 shows a graphical representation showing total chronic insulinsecretion after incubation with and without the cytokine mixture IFN-γ,TNF-α and IL-10 for 1, 2, 3, 5, 8 and 10 days MIN-6 cells (FIG. 25A),Huh7ins cells (FIG. 25B), and Melligen cells (FIG. 25C). Results areexpressed as mean±SE (n=6).

FIG. 26 shows a graphical representation showing insulin storage inMIN-6 cells (FIG. 26A), Huh7ins cells (FIG. 26C), and Melligen cells(FIG. 26C) after incubation with and without the cytokine mixture IFN-γ,TNF-α and IL-1β for 1, 2, 3, 5, 8 and 10 days. Results are expressed asmean±SE (n=5).

FIG. 27 shows a graphical representation showing glucose responsivenessusing a 20 mM glucose stimulus MIN-6 cells with and without treatment(FIG. 27A), Huh7ins cells (FIG. 27B), and Melligen cells (FIG. 27C)after 10 days incubation with the cytokines IFN-γ (384 ng/mL), TNF-α(long/mL) and IL-1β (2000 pg/mL). Results expressed as mean±SE (n=6).Untreated cells (light shade), treated cells (dark shade).

FIG. 28 shows a graphical representation showing a 10-day cytokinetreatment did not affect Huh7ins (FIG. 28A) and Melligen (FIG. 28B)cell's responsiveness to glucose in the millimolar range. Melligen cellssecrete insulin in response to 4.25 mM glucose (the physiological range)and Huh7ins cells to 2.5 mM glucose. Untreated cells (light line),treated cells (dark line).

FIG. 29 is an image of β-cell transcription factors, pancreatichormones, proinsulin convertase, and factors of the glucose sensingapparatus expressed in transfected liver cell lines. RT-PCR analysis forβ-cell transcription factors [PDX-1, NEUROG3, NEUROD1, NKX2-2, NKX6-1,Pax6]; pancreatic hormones [glucagon, somatostatin (SST) and pancreaticpolypeptide (PP)]; GLUT2 and Glucokinase (GK) [islet and liver form];proinsulin convertases [PC1/3 and PC2] in Huh7 cells (lane 1), Huh7inscells (lane 2), Melligen cells (lane 3), human islet (lane 4, thepositive control), and water (lane 5, the negative control).

FIG. 30 shows an image of real-time PCR analysis of Human isletglucokinase in lane 2 human islet cells, lane 3 Melligen cells, lane 4Huh7ins with vector only, lane 5 Huh7ins, lane 6 Huh7 cells, lane 7 dH₂O(FIG. 30A) and human liver glucokinase in lane 2: human islet cells,lane 3: Melligen cells, lane 4: Huh7ins with vector only, lane 5: dH₂O(FIG. 30B). Lane 1: DNA marker in both cases.

FIG. 31 is a graphical representation of real-time PCR expression ofliver GK in Melligen cells and Huh7ins with empty vector (FIG. 31A), andHuh7ins cells and Huh7ins cells with empty vector (FIG. 31B). The levelof gene expression was expressed as the corrected mean Ct value±SE ofindividual cell lines (n=8).

FIG. 32 is a graphical representation of real-time PCR expression ofβ-cell transcription factor, PDX-1: Melligen cells and Huh7ins cells.The level of gene expression was expressed as the corrected mean Ctvalue±SE of individual cell lines (n=8).

FIG. 33 is a graphical representation of real-time PCR expression ofβ-cell transcription factor, NEUROD1: in Melligen cells and Huh7inscells. The level of gene expression was expressed as the corrected meanCt value±SE of individual cell lines (n=8).

FIG. 34 is a graphical representation of Real-time PCR expression of theglucose transporter GLUT2: in Melligen cells and Huh7 cells (FIG. 34A),and Melligen cells and Huh7ins cells (FIG. 34B). The level of geneexpression was expressed as the corrected mean Ct value±SE of individualcell lines (n=8).

FIG. 35 is an image of qualitative western blot analysis for theexpression of PDX-1 in: Huh7 (lane 1), Huh7ins (lane 2), Melligen (lane3), and the positive control, human islet cells (lane 4).

DETAILED DESCRIPTION OF THE INVENTION

The present invention is predicated, in part, on the determination thatglucose responsive insulin secretion by genetically engineered cellswhich are not pancreatic β cells can be more appropriately designed tomimic normal physiological events by engineering the cell to expresspancreatic islet glucokinase, as opposed to other forms of glucokinase.It has been determined that in the absence of the production of thisenzyme, hypersensitive responsiveness to extracellular glucose levelscan occur, leading to the induction of a hypoglycaemic state inindividuals treated with such cells, due to the fact that insulinproduction is upregulated even where systemic levels of glucose arebelow the lower physiological threshold required to stimulate insulinproduction by normal pancreatic β cells. This determination, and thegeneration of cells based thereon, has now facilitated the improvementof therapeutic and prophylactic treatment regimes directed to treatingdiabetes and/or the symptoms associated with diabetes.

Accordingly, one aspect of the present invention is directed to agenetically modified mammalian cell, which cell is capable of secretinginsulin, said genetic modification comprising the transfection of saidcell with a nucleic acid molecule encoding pancreatic islet glucokinase.

Reference to a “cell capable of secreting insulin” should be understoodas a reference to a cell which either does or has the capacity toproduce insulin. Reference to “produce” is a reference to the expression(being transcription and translation) of an insulin encoding nucleicacid molecule and secretion of the insulin expressed thereby. It shouldbe understood, however, that although the cell may be any type ofeukaryotic cell, the cell is not a functionally normal pancreatic βcell. The cell may be one which, even in the absence of the geneticmodification of the present invention can nevertheless produce insulineither constitutively or in response to a stimulus or it is one whichalthough not producing insulin prior to incorporation of the geneticmodification of the present invention, will be able to do so thereafter.

Without limiting the present invention to any one theory or mode ofaction, the capacity of a normal pancreatic β cell to produce insulin ina physiologically relevant glucose responsive manner is due both to itscapacity to express the insulin gene and to the functionality of a“glucose sensing system” which regulates insulin release in response tosmall external nutrient changes. The glucose sensing system essentiallycomprises a high capacity glucose transporter, such as GLUT 2, and aglucose phosphorylation enzyme, such as glucokinase. The lattermolecule, which is the subject of the genetic modification of thepresent invention, provides the crucial cellular functional attributethat ensures that insulin gene expression occurs only in response toextracellular glucose levels which fall within a specific mM range.Without limiting the present invention to any one theory or mode ofaction, insulin is released into the extracellular environment eithervia secretion of soluble insulin by the cell or via anchoring of theinsulin molecules to cell-surface molecules. It should be understoodthat following expression of the nucleic acid molecule encoding insulin,the insulin which is produced may be stored intracellularly for a periodof time prior to its release. For example, the cell may store insulinintracellularly where, upon glucose stimulation, the stored insulin isreleased and/or the expression of insulin is up regulated. This cell maytherefore constitutively express insulin but effects its secretion onlyupon receipt of an appropriate stimulus. To this end, the cell which isthe subject of the genetic modification of the present inventionincludes, but is not limited to:

-   -   (i) cells which naturally express insulin and a functional        glucose sensing system but which require introduction of the        pancreatic islet glucokinase gene in order to effect insulin        production at physiologically relevant extracellular glucose        concentrations (these cells may or may not express an endogenous        glucokinase gene which, although functional, does not meet the        physiological requirements herein discussed);    -   (ii) cells which require some form of genetic or cellular        manipulation in order to enable insulin production and/or        expression of a high capacity glucose transporter. for example,        the cell may require manipulation in order to produce and        secrete insulin (wherein in its natural state that cell would        not produce and/or secrete insulin) or it may require        manipulation in order to enable the cell to produce increased        levels of insulin (wherein in its natural state that cell would        produce and/or secrete lower levels of insulin). Accordingly,        this manipulation may be at the level of the insulin gene and/or        some other gene required to effect insulin production and        secretion, such as a high capacity glucose transporter. Further,        the subject manipulation may be at the level of the insulin or        glucose transporter protein encoding genes or it may be at the        level of a regulatory sequence such as a promoter or enhancer        sequence. The subject cell may therefore inherently exhibit        functionality at the level of one or more aspects of its insulin        production and secretion machinery and may therefore require        manipulation only in relation to some but not all aspects of        this machinery. For example, the cell may be transfected with a        nucleic acid molecule encoding insulin and/or GLUT 2. Even more        preferably, the cell is permanently transfected with cDNA or        genomic DNA encoding insulin and/or GLUT 2. However,        transplantation of cells which transiently express a nucleic        acid molecule encoding these molecules may be useful in certain        circumstances, for example, where the individual will only        temporarily exhibit symptoms of diabetes due to the temporary        down regulation of the activity of their β cells. This may be of        use, for example, in the treatment of transient conditions such        as gestational diabetes. As mentioned earlier, the present        invention should also be understood to extend to the use of        cells in which, rather than transfecting a nucleic acid molecule        encoding insulin into the cell, an endogenous but unexpressed        genomic insulin or glucose transporter gene is switched on, that        is, expression of the gene is induced or even up-regulated where        the gene is not expressed in sufficiently high levels.

In terms of rendering the cell capable of producing and secretinginsulin as detailed above, it would be appreciated that this may haveoccurred at a time point prior to the generation of the cells of thepresent invention or it may occur simultaneously with the geneticmodification of the present invention, being transfection of the cellswith a nucleic acid molecule encoding pancreatic islet glucokinase.

The subject cells may have been freshly isolated from an individual(such as an individual who may be the subject of treatment) or they mayhave been sourced from a non-fresh source, such as from a culture (forexample, where cell numbers were expanded) or a frozen stock of cells(for example, an established stem cell line such as the Huh7ins cellline), which had been isolated at some earlier time point either from anindividual or from another source. It should also be understood that thesubject cells, prior to undergoing the genetic manipulation of thepresent invention, may have undergone some other form of treatment ormanipulation, such as but not limited to enrichment or purification,modification of cell cycle status or the formation of a cell line.Accordingly, the subject cell may be a primary cell or a secondary cell.A primary cell is one which has been isolated from an individual. Asecondary cell is one which, following its isolation, has undergone someform of in vitro manipulation prior to the genetic manipulation of thepresent invention.

In a preferred embodiment, the subject cell is a hepatocyte. Withoutlimiting the present invention to any one theory or mode of action,hepatocytes are known to play a crucial role in intermediary metabolism,synthesis and storage of proteins in the liver. Still further, livercells inherently express the high capacity glucose transporter GLUT 2,this being one of the key elements of the glucose sensing system whichregulates insulin release from pancreatic cells in response to smallexternal nutrient changes. Accordingly, where hepatocytes are used,other than introducing the genetic modification of the present invention(being the incorporation of a gene expressing pancreatic isletglucokinase) they need generally only otherwise be manipulated tointroduce the capacity to express the insulin gene.

The present invention therefore more preferably provides a geneticallymodified mammalian hepatocyte, which hepatocyte is capable of secretinginsulin, said genetic modification comprising the transfection of saidhepatocyte with a nucleic acid molecule encoding pancreatic isletglucokinase.

As detailed hereinbefore, it has been determined that expression of aglucokinase, per se, although enabling cellular glucose responsiveness,may not necessarily result in glucose responsiveness which mimics thephysiological events associated with normal pancreatic functioning. Forexample, the glucokinase enzyme which is endogenously expressed byhepatocytes, although arguably acceptable in the context of normalhepatic functioning, is not ideal in the context of pancreaticfunctioning since it is effectively “hyperresponsive” in that suchcells, if transfected with an insulin encoding gene, will be stimulatedto express and secrete insulin at extracellular glucose concentrationswhich are below those at which normal pancreatic islet β cells wouldproduce insulin. In the context of the human, for example, normalpancreatic islet β cells will produce insulin in response toextracellular concentrations of glucose of the order of 4-5 mM whilesome hepatocytes, if genetically engineered to produce insulin, areresponsive to glucose levels well below 4 mM, thereby exhibiting thepotential to induce hypoglycaemia if not appropriately managed.

To this end, reference to a genetically modified cell which isresponsive to glucose in a “physiologically relevant manner” should beunderstood as a reference to a cell which produces insulin in responseto substantially the same glucose concentration range to which thepancreatic islet β cells of the mammal in issue would normally respond.That is, the subject glucose responsiveness is not such that aphysiologically unacceptable state of hypoglycaemia would be induced tooccur. It would be appreciated, therefore, that this concentration rangemay vary from one mammal to another. In the context of the human, therelevant glucose concentration range is about 4-5 mM of glucose. Interms of overcoming this problem, it has been further determined thatwhere a glucose responsive insulin secreting cell is to be generated,the problem associated with glucose hyperresponsiveness can be overcomeby designing the cell to express pancreatic islet glucokinase. Cellswhich have been transfected with the gene encoding this particular formof glucokinase have been found to achieve a physiological responsivenessto extracellular glucose levels which mimics that observed by normalpancreatic islet β cells.

According to this preferred embodiment, the present invention isdirected to a genetically modified mammalian hepatocyte, whichhepatocyte is capable of secreting insulin, said genetic modificationcomprising the transfection of said hepatocyte with a nucleic acidmolecule encoding pancreatic islet glucokinase and wherein said cell isresponsive to glucose in a physiologically relevant manner.

Reference to “pancreatic islet glucokinase” should be understood as areference to a form of glucokinase which is expressed by pancreaticislet cells. To this end, reference to the proteins which are expressedby the cells of the present invention, such as “insulin”, “glucosetransporter”, “GLUT 2”, “glucokinase” and “pancreatic islet glucokinase”should be understood as a reference to all forms of these proteins andto functional derivatives and homologues thereof. This includes, forexample, any isoforms which arise from alternative splicing of the mRNAencoding these molecules or functional mutants or polymorphic variantsof these proteins. For example, reference to “insulin” should beunderstood as a reference to all forms of insulin including, but notlimited to, precursor forms (for example, proinsulin), split products orpartially cleaved proinsulin (for example des 32,33 insulin and des64,65 insulin), mature insulin (for example, the product obtainedfollowing cleavage of proinsulin) the α or β chain of insulin inisolation or various isoforms of insulin due to the translation of mRNAsplice variants. For example, the Huh7ins cell line produces proinsulinas the bioactive product since liver cells do not naturally express theenzymes PC2 or PC3 which cleave proinsulin to insulin. In anotherexample, the pancreatic islet glucokinase is the human form of thismolecule and, even more preferably, the form encoded by SEQ ID NO:2.

Reference to “mammal” should be understood to include reference to amammal such as but not limited to human, primate, livestock (animal (eg.sheep, cow, horse, donkey, pig), companion animal (eg. dog, cat),laboratory test animal (eg. mouse, rabbit, rat, guinea pig, hamster),captive wild animal (eg. fox, deer). Preferably the mammal is a human orprimate. Most preferably the mammal is a human.

Accordingly, the present invention more preferably provides agenetically modified human hepatocyte, which hepatocyte is capable ofsecreting insulin, said genetic modification comprising the transfectionof said hepatocyte with a nucleic acid molecule encoding pancreaticislet glucokinase.

Preferably, said pancreatic islet glucokinase is human pancreatic isletglucokinase and, even more preferably, the form encoded by SEQ ID NO:2.

“Derivatives” of the molecules herein described (for example insulin,GLUT 2, glucose transporters in general, glucokinase and the like)include functional fragments, parts, portions or variants. Derivativesmay be derived from insertion, deletion or substitution of amino acids.Amino acid insertional derivatives include amino and/or carboxylicterminal fusions as well as intrasequence insertions of single ormultiple amino acids. Insertional amino acid sequence variants are thosein which one or more amino acid residues are introduced into apredetermined site in the protein although random insertion is alsopossible with suitable screening of the functionality of the resultingproduct. Deletional variants are characterised by the removal of one ormore amino acids from the sequence. Substitutional amino acid variantsare those in which at least one residue in a sequence has been removedand a different residue inserted in its place. Additions to amino acidsequences include fusions with other peptides, polypeptides or proteins,as detailed above.

Derivatives also include fragments having particular regions of theentire protein fused to peptides, polypeptides or other proteinaceous ornon-proteinaceous molecules. For example, insulin or derivative thereofmay be fused to another molecule in order to agonise its activity. Inanother example, it may be desirable to facilitate co-expression of bothpro-insulin and a cleavage enzyme. Derivatives of nucleic acid sequenceswhich may be utilised in accordance with the method of the presentinvention may similarly be derived from single or multiple nucleotidesubstitutions, deletions and/or additions including fusion with othernucleic acid molecules. Derivatives of nucleic acid sequences alsoinclude degenerate variants.

A “variant” should be understood to mean a molecule which exhibits atleast some of the functional activity of the form of molecule of whichit is a variant. A variation may take any form and may be naturally ornon-naturally occurring. By “homologue” is meant that the molecule isderived from a species other than that which is being treated inaccordance with the method of treatment aspects of the presentinvention. This may occur, for example, where it is determined that aspecies other than that which is being treated produces a form of thesubject molecule which exhibits suitable functionality. In the contextof insulin, for example, one might utilise the insulin gene of anon-human mammal, even where the cells of the invention are proposed tobe utilised in a human context.

As detailed hereinbefore, the cells of the present invention aregenetically modified. This genetic modification may occur in one or bothof two contexts. First, the cell may have been genetically modified inorder to render it “capable of secreting insulin”. Secondly, the subjectcell is also transfected with a nucleic acid molecule encodingpancreatic islet glucokinase. Accordingly, by “genetically modified” ismeant that the subject cell has undergone some form of molecularmanipulation relative to that which is observed in the context of themajority of a corresponding unmodified population. Such modificationsinclude but are not limited to:

-   -   (i) The introduction of homologous or heterologous nucleic acid        material to the cell. For example, the cell is rendered        transgenic via the introduction of all or part of one or more        genes. This clearly occurs in the context of the transfection of        a nucleic acid molecule encoding pancreatic islet glucokinase        but may also occur to the extent that the cell must be rendered        “capable of secreting insulin”. The genes which are introduced        may encode a protein product, such as insulin, glucokinase or a        glucose transporter. Alternatively, the subject gene may        correspond to a regulatory molecule such as a promoter, for        example where one is merely seeking to modulate the        transcription of an existing gene.    -   Preferably, the cell is transfected with a nucleic acid molecule        encoding insulin or a derivative or homologue thereof. Even more        preferably, the cell is permanently transfected with cDNA or        genomic DNA encoding insulin and/or pancreatic islet glucokinase        or a derivative or homologue thereof. However, cells may be        generated which transiently express a nucleic acid molecule        encoding these molecules. This may be useful in certain        circumstances where, for example, an individual will only        temporarily exhibit symptoms of diabetes due to the temporary        downregulation of the activity of their β cells. This may be of        use, for example, in the treatment of transient conditions such        as gestational diabetes. In another example, rather than        transfecting a nucleic acid molecule encoding these molecules        into the cell, an endogenous but unexpressed genomic gene is        switched on, that is, expression of the gene is induced or even        upregulated where the gene is either not expressed or not        expressed in sufficiently high levels.    -   In addition to the modification of the cells of the present        invention to produce proteins which are directly relevant to        insulin production, other genes relevant to optimising        generation of the subject cells, and which may also be        introduced, include genes encoding marker proteins such as EGFP.        Selection markers, such as antibiotic resistance genes (for        example G418 resistance gene which enables the selection of        mammalian cells using the neomycin analogue G418 or puromycin        resistance gene), provide a convenient means of selecting for        successful transformants while the incorporation of a suicide        gene, such as the pMC1-thymidine kinase gene, facilitates the in        vivo elimination of the introduced genetically modified cells        subsequently to conclusion of the treatment regime. Although        this is not likely to be required in the context of treating        Type I diabetes, it may be relevant where a transient treatment        regime is required such as in the context of gestational        diabetes or some milder forms of Type II diabetes.    -   (ii) The modulation of expression of a gene, for example by        inducing upregulation of expression of a gene which would        otherwise not be expressed, or the mutation of endogenous DNA,        for example to downregulate or render non-functional an unwanted        gene, such as the endogenous hepatic glucokinase gene.

Reference to a “nucleic acid” should be understood as a reference toboth deoxyribonucleic acid and ribonucleic acid thereof. The subjectnucleic acid molecule may be any suitable form of nucleic acid moleculeincluding, for example, a genomic, cDNA or ribonucleic acid molecule. Tothis end, the term “expression” refers to the transcription andtranslation of DNA or the translation of RNA resulting in the synthesisof a peptide, polypeptide or protein. A DNA construct, for example,corresponds to the construct which one may seek to transfect into a cellfor subsequent expression while an example of an RNA construct is theRNA molecule transcribed from a DNA construct, which RNA constructmerely requires translation to generate the protein of interest.Reference to “expression product” is a reference to the product producedfrom the transcription and translation of a nucleic acid molecule.

The term “protein” should be understood to encompass peptides,polypeptides and proteins. It should also be understood that these termsare used interchangeably herein. The protein may be glycosylated orunglycosylated and/or may contain a range of other molecules fused,linked, bound or otherwise associated to the protein such as lipids,carbohydrates or other peptides, polypeptides or proteins (such as wouldoccur where the protein of interest is produced as a fusion protein withanother molecule, for example GST or EGFP). Reference hereinafter to a“protein” includes a protein comprising a sequence of amino acids aswell as a protein associated with other molecules such as amino acids,lipids, carbohydrates or other peptides, polypeptides or proteins.

It would be appreciated by the person of skill in the art that themechanism by which these genetic modifications are introduced may takeany suitable form which would be well known and understood by those ofskill in the art. For example, genetic material is generallyconveniently introduced to cells via the use of an expression construct.Alternatively, one may seek to use, as the starting cellular population,a cell type which either naturally or as a result of earlier random ordirected genetic manipulation is characterised by one or more of thegenetic modifications of interest (for example, one may seek tointroduce the pancreatic islet glucokinase modification into a cellwhich has previously been modified in terms of rendering it “capable ofsecreting insulin”. The modification of a cell line such as Huh7ins, asdiscussed in more detail hereinafter, which is a hepatic cell linetransfected with insulin encoding DNA is one such example).

Most preferably, said genetic modification is the transfection of a cellcapable of secreting insulin with an expression construct comprising oneor more DNA regions comprising a promoter operably linked to a sequenceencoding a pancreatic islet glucokinase and, optionally, a second DNAregion encoding a selectable marker and, optionally, a third DNA regionencoding a suicide protein. In another preferred embodiment, theconstruct may also comprise DNA encoding insulin and/or a glucosetransporter where the subject cell has not previously been rendered“capable of secreting insulin”.

The subject promoter may be constitutive or inducible. Where the subjectconstruct expresses more than one protein of interest, these may beunder the control of separate promoters or they may be under the controlof a single promoter, such as occurs in the context of a bicistronicvector which makes use of an IRES sequence to facilitate the translationof more than one protein product, in an unfused form, from a single RNAtranscript. The subject construct may additionally be designed tofacilitate use of the Cre recombinase mediated splicing inducible geneexpression system.

Reference to a nucleic acid “expression construct” should be understoodas a reference to a nucleic acid molecule which is transmissible to acell and designed to undergo transcription. The RNA molecule is thentranscribed therefrom. In general, expression constructs are alsoreferred to by a number of alternative terms, which terms are widelyutilised interchangeably, including “expression cassette” and “vector”.

The expression construct of the present invention may be generated byany suitable method including recombinant or synthetic techniques. Tothis end, the subject construct may be constructed from firstprinciples, as would occur where an entirely synthetic approach isutilised, or it may be constructed by appropriately modifying anexisting vector. Where one adopts the latter approach, the range ofvectors which could be utilised as a starting point are extensive andinclude, but are not limited to:

-   -   (i) Plasmids    -   Plasmids are small independently replicating pieces of        cytoplasmic DNA, generally found in prokaryotic cells, which are        capable of autonomous replication. Plasmids are commonly used in        the context of molecular cloning due to their capacity to be        transferred from one organism to another. Without limiting the        present invention to any one theory or mode of action, plasmids        can remain episomal or they can become incorporated into the        genome of a host. Examples of plasmids which one might utilise        include the bacterial derived pBR322 and pUC.    -   (ii) Bacteriophage    -   Bacteriophages are viruses which infect and replicate in        bacteria. They generally consist of a core of nucleic acid        enclosed within a protein coat (termed the capsid). Depending on        the type of phage, the nucleic acid may be either DNA (single or        double stranded) or RNA (single stranded) and they may be either        linear or circular. Phages may be filamentous, polyhedral or        polyhedral and tailed, the tubular tails to which one or more        tubular tail fibres are attached. Phages can generally        accommodate larger fragments of foreign DNA than, for example,        plasmids. Examples of phages include, but are not limited to        the E. coli lambda phages, P1 bacteriophage and the T-even        phages (e.g. T4).    -   (iii) Baculovirus    -   These are any of a group of DNA viruses which multiply only in        invertebrates and are generally classified in the family        Baculoviridae. Their genome consists of double-stranded circular        DNA.    -   (iv) Artificial Chromosomes    -   Artificial chromosomes such as yeast artificial chromosomes or        bacterial artificial chromosomes.    -   (v) Hybrid vectors such as cosmids, phagemids and phasmids    -   Cosmids are generally derived from plasmids but also comprise        cos sites for lambda phage while phagemids represent a chimaeric        phage-plasmid vector. Phasmids generally also represent a        plasmid-phage chimaera but are defined by virtue of the fact        that they contain functional origins of replication of both.        Phasmids can therefore be propagated either as a plasmid or a        phage in an appropriate host strain.    -   (vi) Commercially available vectors which are themselves        entirely synthetically generated or are modified versions of        naturally occurring vectors, such as the pIRESpuro3 bicistronic        vector.

It would be understood by the person of skill in the art that theselection of an appropriate vector for modification, to the extent thatone chooses to do this rather than synthetically generate a construct,will depend on a number of factors including the ultimate use to whichthe genetically modified cell will be put. For example, where the cellis to be administered in vivo into a human, it may be less desirable toutilise certain types of vectors, such as viral vectors. Further, it isnecessary to consider the amount of DNA which is sought to be introducedto the construct. It is generally understood that certain vectors aremore readily transfected into certain cell types. For example, the rangeof cell types which can act as a host for a given plasmid may vary fromone plasmid type to another. In still yet another example, the largerthe DNA insert which is required to be inserted, the more limited thechoice of vector from which the expression construct of the presentinvention is generated. To this end, the size of the inserted DNA canvary depending on factors such as the size of the DNA sequence encodingthe protein of interest, the number of proteins which are sought to beexpressed, the number of selection markers which are utilised and theincorporation of features such as linearisation polylinker regions andthe like.

The expression construct which is used in the present invention may beof any form including circular or linear. In this context, a “circular”nucleotide sequence should be understood as a reference to the circularnucleotide sequence portion of any nucleotide molecule. For example, thenucleotide sequence may be completely circular, such as a plasmid, or itmay be partly circular, such as the circular portion of a nucleotidemolecule generated during rolling circle replication (this may berelevant, for example, where a construct is being initially replicated,prior to its introduction to a cell population, by this type of methodrather than via a cellular based cloning system). In this context, the“circular” nucleotide sequence corresponds to the circular portion ofthis molecule. A “linear” nucleotide sequence should be understood as areference to any nucleotide sequence which is in essentially linearform. The linear sequence may be a linear nucleotide molecule or it maybe a linear portion of a nucleotide molecule which also comprises anon-linear portion such as a circular portion. An example of a linearnucleotide sequence includes, but is not limited to, a plasmid derivedconstruct which has been linearised in order to facilitate itsintegration into the chromosomes of a host cell or a construct which hasbeen synthetically generated in linear form. To this end, it should alsobe understood that the configuration of the construct of the presentinvention may or may not remain constant. For example, a circularplasmid-derived construct may be transfected into a cell where itremains a stable circular episome which undergoes replication andtranscription in this form. However, in another example, the subjectconstruct may be one which is transfected into a cell in circular formbut undergoes intracellular linearisation prior to chromosomalintegration. This is not necessarily an ideal situation since suchlinearisation may occur in a random fashion and potentially cleave theconstruct in a crucial region thereby rendering it ineffective.

The nucleic acid molecules which are utilised in the method of thepresent invention are derivable from any human or non-human source.Non-human sources contemplated by the present invention includeprimates, livestock animals (eg. sheep, pigs, cows, goats, horses,donkeys), laboratory test animal (eg. mice, hamsters, rabbits, rats,guinea pigs), domestic companion animal (eg. dogs, cats), birds (eg.chicken, geese, ducks and other poultry birds, game birds, emus,ostriches) captive wild or tamed animals (eg. foxes, kangaroos,dingoes), reptiles, fish, insects, prokaryotic organisms or syntheticnucleic acids.

It should be understood that the constructs of the present invention maycomprise nucleic acid material from more than one source. For example,whereas the construct may originate from a bacterial plasmid, inmodifying that plasmid to introduce the features defined herein nucleicacid material from non-bacterial sources may be introduced. Thesesources may include, for example, viral DNA (e.g. IRES DNA), mammalianDNA (e.g. the DNA encoding the pancreatic islet glucokinase) orsynthetic DNA (e.g. to introduce specific restriction endonucleasesites). Still further, the cell type in which it is proposed to expressthe subject construct may be different again in that it does notcorrespond to the same organism as all or part of the nucleic acidmaterial of the construct. For example, a construct consisting ofessentially bacterial and viral derived DNA may nevertheless beexpressed in the mammalian stem cells contemplated herein.

Without limiting the present invention to any one theory or mode ofaction, the present invention is exemplified in the context of apancreatic islet glucokinase expressing bicistronic vector which istransfected into cells which are already “capable of secreting insulin”in the context of the earlier definition. Specifically, cDNA encodingpancreatic islet glucokinase is transfected into the multicloning siteof pIRESpuro3. Still without limiting the invention in any way, thepIRESpuro3 bicistronic vector exemplified herein contains the internalribosome entry site of the encephalomyocarditis virus, which permits thetranslation of two open reading frames from one messenger RNA (Jacksonet al., 1990, Trends Biochem. Sci. 15:477-483; Jang et al., 1988, J.Virol. 62:2636-2643; Rees et al., 1996, BioTechniques 20:102-104). Afterselection with puromycin, most surviving colonies are likely to stablyexpress the pancreatic islet glucokinase, thus decreasing the need toscreen large numbers of colonies to find functional clones (this being aparticular advantage of bicistronic vectors). To select for cells thatexpress high levels of pancreatic islet glucokinase, the selectivepressure for antibiotic resistance is increased due to the positioningof the puromycin resistance gene downstream to a less optimal positionfor translation as directed by the IRES sequence (Rees et al., 1996,supra). By decreasing the level of expression of the antibioticresistance marker, the selective pressure on the entire expressioncassette is increased, resulting in selection for cells that express theentire transcript, including the pancreatic islet glucokinase, at highlevels. The expression cassette of pIRESpuro3 contains the humancytomegalovirus major immediate early promoter/enhancer followed by amultiple cloning site that precedes stop codons in all three readingframes, a synthetic intron known to enhance the stability of the mRNA(Huang and Gorman, 1990, Nucleic Acids Res. 18:937-947), the ECMV IRESfollowed by the gene encoding puromycin resistance(puromycin-N-acetyl-transferase; de la Luna, et al., 1988, Gene62:121-128), and the polyadenylation signal from SV40. Ribosomes canenter the bicistronic mRNA at the 5′ end to translate the gene ofinterest and at the ECMV IRES to translate the antibiotic resistancemarker. It should be understood that the expression vector exemplifiedherein is provided solely by way of example and is in no way intended tolimit the range and design of vectors which could be used to achieve theobject of the present invention.

The present invention therefore more preferably provides a geneticallymodified human hepatocyte, which hepatocyte is capable of secretinginsulin, said genetic modification comprising the transfection of saidcell with a vector, which vector comprises a nucleic acid moleculeencoding pancreatic islet glucokinase.

Preferably, said vector is a bicistronic vector and said pancreaticislet glucokinase is the form encoded by SEQ ID NO:2.

Even more preferably, said bicistronic vector is pIRESpuro3 and mostpreferably defined by SEQ ID NO:3.

Still more preferably, said genetically modified cell is responsive toglucose in a physiologically relevant manner and, most preferably, toextracellular glucose levels in the range of 3-8 mM, preferably 3.5-7mM, more preferably 4-6 mM and most preferably 4-5 mM.

As would be appreciated by the person of skill in the art, thegeneration of the cells of the present invention may require theapplication of a screening and selection step to identify and isolatecells which have successfully incorporated the genetic modification ofinterest. Identification methods would be well known to the person ofskill in the art and include, but are not limited to:

(i) Detection of specific cellular proteins.

Detection of specific proteins, such as cell surface proteins orintracellular proteins (eg. insulin, GLUT 2, glucokinase etc.), may beconveniently effected via fluorescence affinity labelling andfluorescence microscopy, for example. Briefly, fluorescently labelledantibodies are incubated on fixed cells to detect specific cardiacmarkers. Alternatively, techniques such as Western immunoblotting orhybridization micro arrays (“protein chips”) may be employed. In thisregard, this method can be utilised to identify cell types via either apositive or negative selection step based on the expression of any oneor more molecules.

(ii) Detection of specific cellular RNA or DNA.

This method is preferably effected using RT-PCR or real-time (qRT-PCR).Alternatively, other methods, which can be used include hybridizationmicroarray (“RNA chip”) or Northern blotting or Southern blotting.RT-PCR can be used to detect specific RNAs encoding essentially anyprotein, such as the proteins detailed in point (ii) above, or proteinswhich are secreted or otherwise not conveniently detectable via themethodology detailed in point (ii).

(iii) Detection of specific cellular functional activity.

Although the analysis of a cell population in terms of its functioningis generally regarded as a less convenient method than the screeningmethods of points (i)-(ii), in some instances this may not be the case.For example, to the extent that one is seeking to establish theexistence of a functional glucose sensing system, the insulin output ofa cell of the invention in the presence of varying extracellular glucoselevels may be assessed.

(iv) Other means of screening for the stable integration and maintenanceof the modification (for example in the context of cell line generationand therefore long term cellular culturing) may be performed includescreening for the expression of a selection marker, such as EGFP, whichprovides a most convenient means for establishing the integration of agenetic modification, in particular where marker expression isinextricably linked to the modification of interest, such as via the useof a bicistronic vector.

It should be understood that in terms of characterising the populationof cells generated in the context of the present invention, any one ormore of the techniques detailed above may be utilised.

As detailed hereinbefore, the modified cell of the present invention ispreferably a hepatocyte, this being a cell type which arguably requiresless modification to render it capable of secreting insulin than othercell types due to the fact that it inherently expresses the highcapacity glucose transporter, GLUT 2. However, although hepatocytes alsoinherently express glucokinase, in the context of insulinresponsiveness, this molecule arguably functions in a hypersensitivemanner in that it results in the expression of a transfected insulingene at extracellular glucose levels of as low as 2.5 mM, this beingbelow the physiological range that pancreatic islet cells generallyproduce insulin in the human. Accordingly, the developments of thepresent invention are a significant step forward in that they overcomethis problem.

In accordance with this preferred embodiment, the subject hepatocyte maybe freshly harvested or it may be derived from a cell line. Stillfurther, it may be one which is required to be made capable of secretinginsulin via transfection of the DNA encoding insulin (this occurringeither separately to or concomitantly with the pancreatic isletglucokinase genetic modification herein described) or it may alreadyhave been rendered so. Preferably, said hepatocyte is a Huh7ins cell,this being a cell line which has been modified to express a nucleic acidmolecule encoding insulin. Without limiting the present invention to anyone theory or mode of action, Huh7ins is a genetically engineered livercell line which stores and secretes insulin in response to glucose.However, these cells are hyperresponsive in the physiological sense inthat they can commence secreting insulin at sub-physiological levels ofglucose (eg. 2.5 mM), as compared to between 4-5 mM of glucose fornormal human pancreatic β cell functioning, thereby potentially leadingto the onset of hypoglycaemia. It is thought that these cells exhibit animbalance in the glucokinase:hexokinase ratio in favour of hexokinaseswhich results in enhanced glycolytic flux at low glucose levels andconsequently increased sensitivity of the glucose-stimulated insulinsecretion response. To this end, it has been unexpectedly determinedthat although there exists a functional endogenous glucokinase gene inhepatocytes such as Huh7ins the introduction of the pancreaticglucokinase gene nevertheless acts to overcome the problem associatedwith the endogenous hepatocyte glucokinase gene activity.

The present invention therefore most preferably provides a geneticallymodified Huh7ins cell, said genetic modification comprising thetransfection of said Huh7ins cell with a vector, which vector comprisesa nucleic acid molecule encoding pancreatic islet glucokinase.

Preferably, said vector is a bicistronic vector and said pancreaticislet glucokinase is the form encoded by SEQ ID NO:2.

Even more preferably, said bicistronic vector is pIRESpuro3 and mostpreferably is SEQ ID NO:3.

Still more preferably, said genetically modified Huh7ins cell is aMelligen cell.

The development of the method of the present invention has nowfacilitated the development of means for therapeutically orprophylactically treating disease conditions characterised by aberrant,preferably insufficient or inadequate, production of functional insulin.This problem may be due to any one of a number of causes including, butnot limited to, pancreatic β cell destruction, the aberrant functioningof the cell glucose sensing system, defects in insulin gene expressionor defects in the functionality of the insulin expression productitself. Accordingly, reference to a disease condition “characterised byaberrant production of functional insulin” should be understood as areference to any condition, a symptom or cause of which is insufficientor inadequate levels of functionally effective insulin. Accordingly, andas detailed above, this may be due to defects in the β cell itself, theglucose sensing system or the expression levels or functionality of theinsulin expression product.

Accordingly, another aspect of the present invention is directed to amethod of therapeutically and/or prophylactically treating a conditionin a mammal, which condition is characterised by the aberrant productionof functional insulin, said method comprising introducing into saidmammal an effective number of the genetically modified cellshereinbefore defined.

Preferably, said condition is diabetes.

The present invention therefore more particularly provides a method oftherapeutically and/or prophylactically treating diabetes in a mammal,said method comprising introducing into said mammal an effective numberof the genetically modified cells hereinbefore defined.

Reference to “diabetes” should be understood as a reference to acondition in which insufficient levels of insulin are produced tomaintain biologically normal glucose levels. This may be due tocongenital defects in the pancreatic islet cells, the onset of anautoimmune response directed to the pancreatic β cells (for example type1 diabetes/IDDM, gestational diabetes or slowly progressive IDDM whichis also referred to as latent autoimmune diabetes in adults), defects inthe functioning of the pancreatic islet cells caused by environmentalfactors such as diet or stress (for example type 2 diabetes/adult onsetdiabetes), damage to the pancreatic islet cells such as, but not limitedto, as caused by physical injury, the degeneration of pancreatic isletcells due to non autoimmune conditions or as a side effect due to theonset or treatment of an unrelated disease condition.

In a related aspect of the present invention, the subject undergoingtreatment or prophylaxis may be any human or animal in need oftherapeutic or prophylactic treatment. In this regard, reference hereinto “treatment” and “prophylaxis” is to be considered in its broadestcontext. The term “treatment” does not necessarily imply that a mammalis treated until total recovery. Similarly, “prophylaxis” does notnecessarily mean that the subject will not eventually contract a diseasecondition. Accordingly, treatment and prophylaxis include ameliorationof the symptoms of a particular condition or preventing or otherwisereducing the risk of developing a particular condition. The term“prophylaxis” may be considered as reducing the severity of the onset ofa particular condition. “Treatment” may also reduce the severity of anexisting condition.

The present invention should therefore be understood to encompasspreventing, reducing or otherwise ameliorating diabetes in a mammal.This should be understood as a reference to the prevention, reduction oramelioration of any one or more symptoms of diabetes via the productionof insulin. Symptoms of diabetes include, but are not limited, toabnormal glucose levels or glucose level regulation, abnormal insulinlevels, thirst, frequent urination, weight loss, blurred vision,headache and abdominal pain. It should be understood that the method ofthe present invention may either reduce the severity of any one or moresymptoms or eliminate the existence of any one or more symptoms. Forexample, the method of the present invention may either fully orpartially normalise glucose levels in a diabetic individual. Althoughcomplete normalisation is most desirable, partial normalisation isnevertheless useful, for example, to reduce the risk of a type Idiabetic individual succumbing to a diabetic coma. The method of thepresent invention extends to preventing the onset of any one or moresymptoms of diabetes. For example, in individuals who are predisposed tothe development of diabetes, whose pancreatic islet cells are graduallydegenerating or who have suffered acute and irreparable injury topancreatic islet cells, the method of the present invention may beemployed to restore insulin production prior to the occurrence of anyone or more symptoms of diabetes.

In accordance with this aspect of the invention, the subject cells arepreferably autologous cells which are isolated and genetically modifiedex vivo and transplanted back into the individual from which they wereoriginally harvested. However, it should be understood that the presentinvention nevertheless extends to the use of cells derived from anyother suitable source where the subject cells exhibit the same majorhistocompatability profile as the individual who is the subject oftreatment. Accordingly, such cells are effectively autologous in thatthey would not result in the histocompatability problems which arenormally associated with the transplanting of cells exhibiting a foreignMHC profile. Such cells should be understood as falling within thedefinition of “autologous”. For example, under certain circumstances itmay be desirable, necessary or of practical significance that thesubject cells are isolated from a genetically identical twin, or from anembryo generated using gametes derived from the subject individual orcloned from the subject individual (in this case the cells are likely tocorrespond to stem cells which have undergone directed differentiationto an appropriate somatic cell type). The cells may also have beenengineered to exhibit the desired major histocompatability profile. Theuse of such cells overcomes the difficulties which are inherentlyencountered in the context of tissue and organ transplants.

However, where it is not possible or feasible to isolate or generateautologous cells, it may be necessary to utilise allogeneic cells.“Allogeneic” cells are those which are isolated from the same species asthe subject being treated but which exhibit a different MHC profile.Although the use of such cells in the context of therapeutics wouldlikely necessitate the use of immunosuppression treatment, this problemcan nevertheless be minimised by use of cells which exhibit an MHCprofile exhibiting similarity to that of the subject being treated, suchas a cell population which has been isolated/generated from a relativesuch as a sibling, parent or child. Also contemplated herein is the useof established cell lines such as Huh7ins or the Melligen cells whichhave been derived therefrom. The present invention should also beunderstood to extend to xenogeneic transplantation. That is, the cellswhich are genetically modified in accordance with the method of theinvention and introduced into a patient are isolated from a speciesother than the species of the subject being treated.

Reference to an “effective number” means that number of cells necessaryto at least partly attain the desired effect, or to delay the onset of,inhibit the progression of, or halt altogether the onset or progressionof the particular condition being treated. Such amounts will depend, ofcourse, on the particular condition being treated, the severity of thecondition and individual patient parameters including age, physicalconditions, size, weight, physiological status, concurrent treatment,medical history and parameters related to the disorder in issue. Oneskilled in the art would be able to determine the number of cells of thepresent invention that would constitute an effective dose, and theoptimal mode of administration thereof without undue experimentation,this latter issue being further discussed hereinafter. These factors arewell known to those of ordinary skill in the art and can be addressedwith no more than routine experimentation. It is preferred generallythat a maximal cell number be used, that is, the highest safe numberaccording to sound medical judgement. It will be understood by those ofordinary skill in the art, however, that a lower cell number may beadministered for medical reasons, psychological reasons or for any otherreasons.

As hereinbefore discussed, it should also be understood that althoughthe method of the present invention is predicated on the introduction ofgenetically modified cells to an individual suffering a condition asherein defined, it may not necessarily be the case that every cell ofthe population introduced to the individual will have acquired or willmaintain the subject modification. For example, where a transfected andexpanded cell population is administered in total (i.e. the successfullymodified cells are not enriched for), there may exist a proportion ofcells which have not acquired or retained the genetic modification. Thepresent invention is therefore achieved provided the relevant portion ofthe cells thereby introduced constitute the “effective number” asdefined above. However, in a particularly preferred embodiment thepopulation of cells which have undergone differentiation will besubjected to the identification of successfully modified cells, theirisolation (for example by EGFP based FACS sorting or GST selection) andtesting for a functional genetic modification and introduction to thesubject individual. This provides a means for selecting a specificsubpopulation of cells for administration, such as cells expressingappropriate levels of the insulin and glucose sensing molecules inissue.

In the context of this aspect of the present invention, the subjectcells require introduction into the subject individual. To this end, thecells may be introduced by any suitable method. For example, cellsuspensions may be introduced by direct injection or inside a blood clotwhereby the cells are immobilised in the clot thereby facilitatingtransplantation. The cells may also be encapsulated prior totransplantation. Encapsulation is a technique which is useful forpreventing the dissemination of cells which may continue to proliferate(i.e. exhibit characteristics of immortality), although this is notexpected to be a significant problem where a pure population ofterminally differentiated cells are administered (but may be an issue ifthe cell population is derived from an immortalised cell line) or forminimising tissue incompatibility rejection issues.

The cells may also be introduced by surgical implantation. This may benecessary, for example, where the cells exist in the form of a tissuegraft or where the cells are encapsulated prior to transplanting. Thesite of transplant may be any suitable site, for example, subcutaneouslyor, where the donor cells are liver cells, under the renal capsule.Without limiting the present invention to any one theory or mode ofaction, where cells are administered as an encapsulated cell suspension,the cells will coalesce into a mass. It should also be understood thatthe cells may continue to divide following transplantation.

The cells which are administered to the patient can be administered assingle or multiple doses by any suitable route. Preferably, and wherepossible, a single administration is utilised. Administration viainjection can be directed to various regions of a tissue or organ,depending on the type of treatment required.

In accordance with the method of the present invention, otherproteinaceous or non-proteinaceous molecules may be coadministeredeither with the introduction of the insulin-producing cells or duringinsulin production by the transplanted cells. By “coadministered” ismeant simultaneous administration in the same formulation or indifferent formulations via the same or different routes or sequentialadministration via the same or different routes. By “sequential”administration is meant a time difference of from seconds, minutes,hours or days between the transplantation of these cells and theadministration of the proteinaceous or non-proteinaceous molecules orthe onset of insulin production and the administration of theproteinaceous or non-proteinaceous molecule. For example, it may benecessary to co-administer the enzyme PC2 or PC3 to facilitate cleavageof proinsulin to insulin. Other examples of circumstances in which suchco-administration may be required include, but are not limited to:

-   -   (i) When administering non-syngeneic cells or tissues to a        subject, there usually occurs immune rejection of such cells or        tissues by the subject. In this situation it would be necessary        to also treat the patient with an immunosuppressive regimen,        preferably commencing prior to such administration, so as to        minimise such rejection. Immunosuppressive protocols for        inhibiting allogeneic graft rejection, for example via        administration of cyclosporin A, immunosuppressive antibodies,        and the like are widespread and standard practice.    -   (ii) Depending on the nature of the condition being treated, it        may be necessary to maintain the patient on a course of        medication to alleviate the symptoms of the condition until such        time as the transplanted cells become integrated and fully        functional (for example, the administration of insulin).        Alternatively, at the time that the condition is treated, it may        be necessary to commence the long term use of medication to        prevent re-occurrence of the damage. For example, where the        subject damage was caused by an autoimmune condition, the        ongoing use of immunosuppressive drugs may be required even when        syngeneic cells have been used. This will depend, however, on        the nature of the cells which have been genetically modified and        whether or not they would correspond to an autoimmune target.

It should also be understood that the method of the present inventioncan either be performed in isolation to treat the condition in issue orit can be performed together with one or more additional techniquesdesigned to facilitate or augment the subject treatment. Theseadditional techniques may take the form of the co-administration ofother proteinaceous or non-proteinaceous molecules, as detailedhereinbefore.

Although the method of the present invention is particularly suited tothe treatment or prophylaxis of diabetes, it is not to be understood asbeing limited to the treatment of this condition. Rather, the method ofthe present invention can be utilised to treat any conditioncharacterised by aberrant, unwanted or otherwise inappropriatefunctional activity or levels of a molecule which is directly orindirectly modulatable by insulin, such as but not limited to, thelevels of glucose and/or insulin or derivative or equivalent thereof.Reference to “aberrant, unwanted or otherwise inappropriate” functionalactivity or levels of such a molecule (for example, glucose and/orinsulin) should be understood as a reference to either permanently ortransiently abnormal levels or activities of these molecules or tophysiologically normal levels or activities of one or both of thesemolecules, which levels or activities are nevertheless unwanted orotherwise inappropriate.

It should be understood that a molecule which is “directly” modulatableby insulin is one which the subject insulin associates or otherwiseinteracts with to up-regulate, down-regulate or otherwise modulate itsfunctional activity or levels or to in any way alter its structural orother phenotypic, molecular or other physical features. Increasinginsulin levels, per se, should be understood to fall within the contextof this definition. A molecule which is “indirectly” modulatable byinsulin is one which is modulated (in the context described above) by aproteinaceous or non-proteinaceous molecule other than insulin, whichother proteinaceous or non-proteinaceous molecule is directly orindirectly modulated by said insulin. Accordingly, the present inventionextends to the modulation of the functional activity or levels of agiven molecule via an insulin induced cascade of regulatory steps.

Another aspect of the present invention contemplates a method ofmodulating insulin levels in a mammal said method comprising introducinginto said subject an effective number of the genetically modified cellshereinbefore defined.

Yet another aspect of the present invention contemplates a method ofmodulating glucose levels in a mammal said method comprising introducinginto said subject an effective number of the genetically modified cellshereinbefore defined.

Still another aspect of the present invention is directed to the use ofgenetically modified cells hereinbefore defined in the manufacture of amedicament for the treatment of a condition in a mammal, which conditionis characterised by the aberrant production of functional insulin.

Preferably, said condition is diabetes.

The development of the cells of the present invention has nowfacilitated the development of in vitro based screening systems fortesting the effectiveness and toxicity of existing or potentialtreatment or culture regimes.

Thus, according to yet another aspect of the present invention, there isprovided a method of assessing the effect of a treatment or cultureregime on the phenotypic state of the genetically modified cells ashereinbefore defined, said method comprising subjecting said cells tosaid treatment regime and screening for an altered phenotypic state.

By “altered” is meant that one or more of the phenotypic or functionalparameters which are the subject of analysis are changed relative tountreated cells. This may be a desirable outcome where the treatmentregime in issue is designed to improve or assist cellular functioning.However, where the treatment regime is associated with a detrimentaloutcome, this may be indicative of toxicity and therefore theunsuitability for use of the treatment regime. It is now well known thatthe differences which are observed in terms of the responsiveness of anindividual to a particular drug are often linked to the unique geneticmakeup of that individual. Accordingly, the method of the presentinvention provides a valuable means of testing either an existing or anew treatment regime which may be used concurrently with theadministration of the cells of the invention. This provides a uniquemeans for evaluating the likely effectiveness of a drug, such as a drugwhich is proposed to be co-administered with the cells of the invention,prior to administering the drug and the cells in vivo. Where a patientis extremely unwell, the physiological stress which can be caused by atreatment regime which causes an unwanted outcome can be avoided or atleast minimised.

Accordingly, this aspect of the present invention provides a means ofoptimising a treatment regime.

Hence the method of the present invention can be used to screen and/ortest drugs, other treatment regimes or culture conditions. In thecontext of assessing phenotypic or functional changes, this aspect ofthe present invention can be utilized to monitor for changes to the geneexpression profiles of the subject cells and tissues. Thus, the methodaccording to this aspect of the present invention can be used todetermine, for example, gene expression pattern changes in response to aproposed concomitant treatment regime, such as a treatment regime whichis required to be maintained in order to treat an unrelated conditionfrom which the patient also suffers.

Preferably, the treatment to which the cells or tissues of the presentinvention are subjected is the exposure to a compound. Preferably, thecompound is a drug or a physiological ion. Alternatively the compoundcan be a growth factor or differentiation factor. To this end, it ishighly desirable to have available a method which is capable ofpredicting such side effects on the cells of the invention prior totheir exposure to the drug.

The present invention is further defined by the following non-limitingExamples.

Example 1 Generation and Testing of Melligen Cells Materials and MethodsPlasmid Construct

Human islet glucokinase cDNA contained in the pBluescript commercialvector, was a gift from Dr M. Alan Permutt, the University of Washington(St Louis, USA). The human islet glucokinase cDNA was cut out of thepBrescript SK+ by restriction enzyme E_(COR) I. The 2733 base pairfragment containing the human islet glucokinase cDNA was inserted intothe pIERSpuro3 expression vector (Clontech, USA) at the E_(COR) I sitein the multi cloning site (971-972 bp) (FIG. 1).

Cell Culture

Huh7ins cells were cultured as monolayers in Dulbecco's Modification ofEagles's Medium containing 10% fetal calf serum (FCS) in 5% CO₂ in airplus 0.55 mg/ml G418 as described (Tuch et al., 2003, Gene Therapy10:490-503).

Transfection of Plasmid with Human Islet Glucokinase cDNA

Huh7ins cells were transfected with the pIRESpuro3-glucokinase constructor the pIRESpuro3 vector alone using Effectenen transfection reagent(Qiagen Germany). Twenty four hours after transfection the eukaryocidalantibiotic puromycin (1.1 μg/ml) was added to the cultures. Medium plusdrugs were changed every 2-3 days. After 14 days of selection, colonieswere picked up and expanded into mass cultures. The cells containing thepIRESpuro3-glucokinase construct will hereafter be referred to asMelligen cells.

Human Islet Glucokinase cDNAs Identification

Total RNA was isolated from clonal cell lines using the Triazol™ methodaccording to the manufacturer's instructions (Gibco-BRL). The RNA samplewas treated with DNase in 20m Tris-HCl (pH 8.4), 2 mM MgCl₂, and 50 mMKCl to remove any traces of contaminating genomic DNA. cDNA wassynthesised using a transcription kit (Qiagen, Germany). The RT-PCR wasundertaken in a volume of 30 μl of buffer containing 50 mM KCl, 10 mMTris-HCl, 3.5 mM MgCl₂, 200 μM each dNTPs, 0.4 μM of the primers and 0.5ug cDNA.

The primers designed for human islet glucokinase cDNA were as follows:5′-CTGAGTGGCTTGTGATTCTG-3′ (SEQ ID NO:4); 5′-AATCTTAGGTTGGGCATGG-3′ (SEQID NO:5), which yields a 220 bp product (2461-2681 base pairs).

Amplification was undertaken for 35 cycles at denaturing temperature 95°C. for 45 seconds, annealing temperature 56° C. for 30 seconds andextension temperature 72° C. for 35 seconds. The PCR product wasseparated on 2% agarose gel with TBE buffer (FIG. 3).

Western Blot Analysis

Melligen cells, Huh7ins with empty vector and Huh7ins cells weretrypsinised and removed from tissue flasks. The suspended cells werecentrifuged at 1000 rpm for 5 minutes and supernatant was aspirated. Thecell pellets were suspended with buffer I (Tris 10 mM, NaH₂PO₄ 20 mM,EDTA 1.0 mM, PMSF 0.1 mM, pepstatin 10 μg/ml, leupeptin 10 μl/ml atpH=7.8) and applied the freeze (−70° C., 10 minutes)-thaw (37° C., 10minutes) cycle three times, then incubated for 20 minutes at 4° C.Supernatants were prepared by centrifugation at 11,000 rpm in arefrigerate microfuge for 30 minutes and the protein concentration insupernatant was subsequently determined using the Micro BCA proteinAssay Reagent Kit (PIERCE).

Protein samples from the three different cell types (15 μg/30 μl) wererun on 10% polyacrylamide gels for Western blot analysis at 100v andthen transferred to a nitrocellulose membrane (Millipore Corporation,USA). The nitrocellulose membrane was blocked in phosphate bufferedsaline (PBS) with 5% skim milk overnight at 4° C. to avoid anynon-specific binding. After washing three times (10 min) with PBScontaining 0.05% Tween₂₀. The nitrocellulose membrane was incubated withprimary antibody—rabbit anti-human glucokinase antibody ( 1/1000dilution) (Santa Cruz Biot USA) for 2 hours at room temperature, thenwashed again three times with PBS (0.05% Tween₂₀), the nitrocellulosemembrane was incubated with second antibody—a polyclonal (donkey)anti-rabbit horseradish peroxidase IgG conjugate ( 1/800 dilution)(Sigma) for 1 hour at room temperature. After washing three times withPBS (0.05% Tween₂₀), glucokinase protein expression in thenitrocellulose membrane was detected using 3,3′-Diaminobenzidine(peroxidase substrate) (Sigma). The primary human glucokinase was raisedin rabbits against a recombinant protein corresponding to amino acids318-405 mapping near the carboxy terminus of glucokinase of humanorigin, conjugated to a monoclonal anti-rabbit IgG antibody and detectsa protein of 52 kD (FIG. 4).

Glucokinase and Hexokinase Enzyme Activity

Glucose phosphorylation was measured in cell homogenates by followingthe conversion of [U-¹⁴C] glucose to [U-¹⁴C] glucose-6-phosphate asdescribed (Kuwajima et al., 1996, J Biol. Chem. 261: 8849-53).Glucokinase and hexokinase activities were discriminated by performingthe assay in the presence or absence of 10 mmol/L glucose-6-phosphate,an inhibitor of low K_(m) hexokinase activity (Wilson, 1984, Regulationof carbohydrate metabolism, p. 45-85).

Qualitative western analysis showed the presence of human glucokinase inall cell lines tested, but their appeared to be an upregulation of theprotein in the Melligen cells (FIG. 4). Huh7, Huh7ins and Huh7ins emptyvector cells contain 16±1.2, 24.2±2.3, 25.4±2.6 U/g protein of glucosephosphorylating activity, respectively when assayed at 20 mM glucose inthe absence of glucose-6-phosphate, but this activity is reduced to3.0±0.5, 4.8±0.4 and 4.7±0.5 U/g protein respectively when the assay isconducted in the presence of 10 mmol/1 glucose-6-phosphate (FIG. 5).This indicates that most of the glucose-6-phosphate activity iscontributed by low K_(m) glucose-6-phosphate sensitive hexokinases inthe Huh7 cell lines. By comparison Melligen cells have a significantlyhigher (P<0.01) level of glucose-phosphorylating capacity compared tothe other cell lines when measured in the absence of glucose-6-phosphateof 34.6±3.4 U/g protein, which correlates with the increased proteinconcentration in the western blot. However, in the presence ofglucose-6-phosphate Melligen cells exhibit a 3-fold enhancement inactivity: 20.6±2.7 U/g, over the Huh7ins cells, therefore in Melligencells hexokinase activity represents ‘42% of the total glucosephosphorylating capacity, with the remainder contributed byglucose-6-phosphate-insensitive glucokinases.

Acute Stimulation of Insulin Secretion

Before stimulation, 5×10⁶ cells (Huh7, Huh7ins with the vector only andMelligen cells) were plated into each well of a six well plateovernight, then tissue culture plates were thoroughly washed with basalmedium (PBS containing 1 mM CaCl₂ and supplemented with 20 mM HEPES and2 mg/ml BSA, 1.25 mM glucose) to remove culture medium and FCS.Monolayers were incubated in the basal medium at pH 7.4 for twoconsecutive periods of 1 hour to stabilize the basal secretion ofinsulin. Monolayers were then exposed to stimuli for 1 hour. Glucose,1.25-20 mM was dissolved in basal medium. Basal medium alone was used asa control. In response to increasing concentrations of glucose from 1-20mM, a dose-response curve for insulin secretion was generated for anumber of Melligen cell clones and compared with that for the parentHuh7ins cells. It can be seen in FIG. 6 that while glucoseresponsiveness commenced at 2.5 mM in Huh7ins cells, it commenced in thephysiological range between 4-5 mM in the Melligen cells. The actuallevel of insulin secreted to glucose in the physiological range was alsodouble that of the parent Huh7ins cells in clone 6 cells, which wereused in all subsequent experiments, Assay of Huh7ins cells with vectoralone were not significantly different from the Huh7ins cells (resultsnot shown). Further experiments determined the exact concentration ofglucose at which Huh7ins-GK cells commenced glucose-responsive insulinsecretion to be 4.25 mM (FIG. 7).

Insulin Secretion and Storage

Huh7ins with the vector only and Melligen cells were washed with PBS,trypsinised and removed from tissue culture flasks. The suspended cellswere centrifuged at 1000 rpm for 5 minutes and supernatant wasaspirated. The cells were resuspended in the desired volume of freshmedium, a cell count was performed and the cells were distributed into1.5 ml tubes at a density of 5×10⁶ cells per tube. The tubes werecentrifuged at 1800 rpm for 5 minutes and the supernatant was discarded.The cells were resuspended in 300 μl of 0.18N HCL in 70% ethanol for 48hours at 4° C., to allow sufficient time for lysis of cells and releaseof stored insulin. For measurement of insulin content, samples werediluted in 1:10 before being placed in the radioimmunoassay (MA).

Insulin Secretion Test (RIA Assay)

Levels of human insulin were measured by a RIA specific for this peptideand its split products as described previously (Tuch et al., 2003, GeneTherapy 10:490-503). Specificity was established by showing <0.05%cross-reactivity with insulin. The insulin MA was carried out usingguinea pig insulin antibody (Wellcome, England) and ¹²⁵I-labelledinsulin prepared by the chloramine-T method. Cross-reactivity with humanproinsulin was 73%. Human insulin standards were used to assay theproduct from liver cells.

Transmission and Immuno Electron Microscopy

For morphological analysis by electron microscopy, Melligen cells werefixed (2% glutaraldehyde/1% paraformaldehyde) and processed according toconventional techniques using uranyl acetate block staining andReynold's lead citrate counter-staining of ultrathin sections (80 nm).Stained sections were examined at 80 kV on a Phillips CM 10 transmissionelectron microscope. Granule size was measured directly from the imagesafter calibrating with replicas (FIG. 8a ).

For immunoelectronmicroscopy, a post-embedding immunogold procedure wasused to confirm the localization of intracellular insulin. Single cellsuspensions of Melligen and MIN-6 cells (mouse insulinoma cell line,used as a positive control) were analyzed. Briefly, the sections wereincubated in 50% sodium metaperiodate at 50° C. for 3.5 minutes followedby 0.01M sodium citrate buffer pH 6.0 at 95° C. for 10 minutes and a 15minute cooling period. Non specific binding was blocked using 1% goatserum for 30 minutes at room temperature. A goat anti guinea pig 10 nm(1:50) gold probe (Aurion, Wageningen, The Netherlands) incubated for 2hours at room temperature was directed against a polyclonal guinea piganti human insulin (1:20) primary antibody (Zymed, San Francisco, USA)incubated overnight at 4° C. Primary antibody was replaced by PBS toassess the level of non specific binding of the gold probe. Sectionswere counter-stained with Reynold's lead citrate prior to examination(FIG. 8b ).

Statistical Analysis

Data were expressed as means±S.E. Paired sample means were compared withStudent's t-test.

Results

FIG. 2 shows the sequence of the pIERSpuro3 vector (5157 base pairssequence) with insert human islet glucokinase cDNA (2733 base pairs),which was cloned into the vector at the 972 bp site. Both junctions ofthe vector and insert have been sequenced (results not shown).

Example 2 Melligen Cells can Correct Diabetes by Retaining InsulinSecretory Responsiveness to Glucose Stimulation In Vivo

In vivo glucose responsiveness in the millimolar concentration range isthe hallmark of an artificial β cell for insulin replacement therapy inType 1 diabetes. Where this can be achieved, such artificial β cellsoffer a potential strategy to overcome the limited availability of humanpancreatic donor tissue. The survival of unencapsulated Huh7ins cells ina diabetic immunodeficient mouse model has been demonstrated.

To test the feasibility of Melligen cells to correct the diabetic statewithout inducing hypoglycaemia, Melligen cells (10⁷ cells) aretransplanted subscapularly into non-autoimmune non-obese diabetic severecombined immunodeficiency (NOD.scid) mice. Groups of eight animals arerequired for these experiments. Diabetes (blood glucose levels exceeding14 mM on two separate occasions and serum insulin concentration below0.15 ng/mL) is induced by a single high dose of STZ (250 mg/kg bodyweight). After transplantation, body weight and blood glucose ismonitored three times each week and then daily if blood glucoseconcentrations decrease below 4 mM. Transplantation is consideredsuccessful if the non-fasting blood glucose concentration returns tonormal (less than 8.4 mM) within 5 days after surgery. Animals aremaintained on exogenous insulin immediately after transplantation ifnecessary. Transplants are considered unsuccessful if the blood glucoseconcentration increases to more than 20 mM on more than two occasions.After transplantation and when blood glucose levels are between 5 and 10mM, glucose tolerance tests are performed and blood glucose and seruminsulin levels assayed. If blood glucose levels fall to less than 2 mMfor more than 24 h the animal is sacrificed and the transplant removed.If the normoglycaemic state is retained, then explants will be harvestedat 2, 6 and 12 weeks after transplantation from a cohort to verify thathyperglycaemia subsequently returns. At 2, 6, and 12 weeks pancreas isprepared for insulin immunohistochemistry. After resection, the graft isweighed and the proliferative characteristics of Melligen cellsquantified by MTT assay over a period of 72 h. The insulin content ofthe graft is measured. Explants are also examined for gene expression(of glucokinase, GLUT2 glucose transporter, and insulin by PCR),histologically (for cellular integrity, insulin secretory granules, andvascularisation) and immunohistochemically (for insulin).

Example 3 Microencapsulation Melligen Cells to Provide a Means ofEctopic Insulin Production and Secretion Both (A) In Vitro and (B) InVivo with the Avoidance of Autoimmune Destruction (a) In VitroExperiments Using Encapsulated Melligen Cells

Melligen cells are microencapsulated and then cultured in vitro for upto 6 weeks. Viability and glucose responsiveness of encapsulatedMelligen cells are determined after 1, 2, 4 and 6 weeks in culture priorto commencing any in vivo studies using microencapsulated cells. A doseresponse curve for insulin secretion in response to glucose from basalto high glucose levels of the encapsulated cells is established. Chronicand acute insulin release by the encapsulated cells is determined. Tomeasure acute insulin release, static incubations are carried out withtraditional stimuli (glucose, theophylline, and 8-Br-cAMP [whichincreases intracellular cAMP]). Insulin storage is also examined aftersonication and extraction overnight in acid ethanol. Insulin storage andsecretion is measured by insulin RIA as previously described (Tuch, etal., 2003, Gene Therapy 10:490-503; Permutt et al., 1989, Proc Natl AcadSci USA, 86:8688-8692). The percentage of live and dead cells isidentified by observing calcein and propidium iodide fluorescence,respectively, using a confocal microscope. Among the cytotoxic factorswhich are responsible for limited survival of encapsulated grafts themost important are thought to be cytokines. To determinecytokine-induced Melligen cell destruction, unencapsulated andmicroencapsulated cells are co-cultured with pro-inflammatory cytokines.Encapsulated Melligen cells are with activated human macrophage celllines and viability and insulin secretion subsequently determined.

(b) In Vivo Experiments Using Encapsulated Melligen Cells

(i) Evaluation of Biocompatibility of Microcapsules

For this therapy to become clinically viable, the microcapsules must notprovoke excessive cellular overgrowth, which would limit the diffusioncapacity and the life span of the transplant. Therefore, emptymicrocapsules are transplanted subscapsularly into 6-week-old non-obesediabetic (NOD) mice that have not yet developed spontaneous diabetes. At2, 6, and 12 weeks after transplantation, the microcapsules is removedand the degree of capsular overgrowth determined.

(ii) Transplantation of Encapsulated Melligen Cells

Encapsulated Melligen cells are analysed to determine if they canreverse autoimmune diabetes without the subsequent development ofhypoglycaemia. Spontaneously diabetic NOD mice are used for theseexperiments. Correction of diabetes is ascertained by the same scenarioas for unencapsulated Melligen cells and glucose tolerance tests areperformed. Capsules are removed 2, 6, and 12 weeks after transplantationand examined for capsular overgrowth and explanted capsules are alsoevaluated for insulin secretion in response to glucose, insulin content,and viability (MTT assay) and immunohistological examination.

(iii) Immunoreactivity of Encapsulated Melligen Cells

Results indicate that that unlike pancreatic β cells, insulin-expressingliver cells may not be susceptible to autoimmune destruction. However,inflammatory reactions may be generated if antigenic products fromencapsulated dying cells diffuse through the microcapsule. Therefore, ananalysis is performed to determine if microcapsules preventcommunication between Melligen cells and immune cells that might causelymphocyte activation. This is achieved using a conventional splenocyteco-culture system. IgG deposition is also assessed on the microcapsulesand the Melligen cells contained in the microcapsules (after incubationof microcapsules with FITC-labelled anti-mouse IgG antibody) at 6 and 12weeks after transplantation, to determine if antibodies are induced byeither antigens shed from the cell surface, proteins secreted by livecells, or liberated after cell death that may diffuse through thecapsule.

Example 4 Resistance of Insulin Secreting Liver Cell Line toPro-Inflammatory Cytokines Involved in Beta Cell Death Results

Preliminary experiments were conducted to determine appropriatedilutions of the cytokines, IFN-γ, TNF-α and IL-1β, that would reduceviability in the control β-cell line, MIN-6. Cytokines were also testedfor efficacy both individually and in combination according to theexperimental design of Tabiin et al. (2001). The MTT assay for cellviability was employed to determine the cytotoxic effect of cytokines onHuh7ins cells, Melligen cells, and the parent cell line, Huh7. AnnexinV/PI staining allowed detection of necrotic and apoptotic populations incytokine treated and untreated cells.

Characterisation of Cell Growth

To establish the growth kinetics of each of the cell lines (MIN-6, Huh7,Huh7ins and Melligen) used in this study, cell numbers were quantifiedover varying periods of time. An initial seeding density of 1×10⁴cells/mL in 6 well plates was used, based on previous experiments, andgrowth curves were generated. Each of the cell lines reached stationaryphase at different rates (FIG. 9). Huh7, Huh7ins and Melligen cellsapproached exponential growth by day 8 when the cell concentration wasapproximately 1×10⁶ cells/well. In contrast, MIN-6 cells only reached acell concentration of 5×10⁵ cells/mL at the same time-point (FIG. 9). Itwas also found that the highest recorded cell number for the MIN-6 cells(1×10⁶ cells/mL) was only reached at day 10. As MIN-6 and Huh7 cells areof murine pancreatic and human liver origin, respectively, each cellline exhibited distinct growth kinetics. These cell growthcharacteristics were used to determine the time course for experimentsin which cytokines were co-incubated with cell lines. Since MIN-6 cellsreached the log growth phase at a later time point, this cell line wasplated at higher seeding densities when run in parallel experiments withHuh7 and Huh7ins to ensure that the cells were in log phase when used inthe cytokine toxicity experiments.

As the MTT assay was to be used to determine cell viability in both thepresence and absence of cytokines, preliminary experiments wereperformed to determine cell viability of untreated Huh7ins cells.Huh7ins cells were seeded at an initial density of 1×10³ cells/well intoa 96-well plate and cultured for 8 days. In the MTT assay, MTT ismetabolised by mitochondrial dehydrogenase within the viablemitochondria of a cell to produce a purple coloured crystal, formazan.When dissolved in DMSO the absorbance of the formazan solution can beread at 570 nm. The MTT assay is a rapid and reproducible method fordetermining cellular response to cytotoxic agents.

The results obtained from this preliminary experiment showed that theseeding density chosen approached an absorbance value of 1.0 nm over the8-day period. The initial seeding density used was optimal sincesubsequent experiments to assess the cytotoxic effect of cytokines wereto be conducted for between six and twelve days. These results alsoshowed that the exponential growth of the cells was reflected by themitochondrial activity of the cells. From the growth kinetic results(FIG. 11) it was also determined that MIN-6 cells would be plated attwice the seeding density as the liver cell lines.

Optimisation of Cytokine Treatment on MIN-6 Cells by the MTT Assay

Initial experiments used serial dilutions of single cytokineconcentrations of IFN-γ, TNF-α and IL-1β. The ED₅₀ (effective doserequired to destroy half the cell population) indicated on therespective data sheet for each cytokine constituted the most diluteconcentration used (Table 1). These initial titration experiments werenecessary as each ED₅₀ value provided on the data sheets applies to aspecific application and a specific cell line. Additionally, differentpreparations of cytokines exhibit differing potencies.

TABLE 1 OPTIMISATION OF SINGLE CYTOKINE CONCENTRATIONS FOR MIN-6 CELLSIFN-γ TNF-α IL-1β ng/mL ng/mL ng/mL 19.2 5.00 0.50 9.60 2.50 0.25 4.801.25 0.125 2.40 0.63 0.063 1.20 0.31 0.031 0.60 0.16 0.016 0.30 0.080.008 0.15 0.04 0.004

Results from the MTT assay revealed that co-incubation of MIN-6 cellswith the concentrations of single cytokines at the concentrations listedin Table 1 did not reduce the viability of MIN-6 cells as compared tountreated cells even after 14 days of co-incubation (data not shown).Consequently, the cytokines were used in combination and at highercytokine concentrations. The concentrations employed were similar tothose used by Tabiin et al. (2001) in studies investigating the cytokinetreatment of both the rodent insulinoma cell line, NIT-1, and theinsulin secreting human hepatocyte cell line, HEPG2 ins/g.

Media and cytokines IFN-γ (384 ng/mL), TNF-α (long/mL) and IL-1β (2000pg/mL) singly and in combination were changed once every two days andcells were assayed for viability over a six-day period. However, at theinitial seeding density used (2×10³ cells/well), approximately 43±2% ofMIN-6 cells were still viable at the final day of the experiment (FIG.9a ). The observation period was therefore increased to 8 days and themedia and cytokines were changed daily. Under these conditions, by day8, only 22±1% of MIN-6 cells were viable as compared to 100±1% foruntreated cells (P=0.0045) (FIG. 9b ).

As it was preferable to obtain the lowest percentage of viable cells bythe final day of the experiment and to precisely determine the kineticsof cytokine induced death, the triple cytokine combination concentrationwere further titrated by adding the cytokines at twice IFN-γ (768ng/mL), TNF-α (20 ng/mL) and IL-1β (4000 pg/mL) and half the triplecytokine concentrations IFN-γ (192 ng/mL), TNF-α (5 ng/mL) and IL-1β(1000 pg/mL) previously used.

After changing cytokines daily at the concentrations used in FIGS. 10aand b , approximately 20±2% of the cells still remained viable comparedto 100±2% viability of the control cells (P=0.0065). Application ofsingle cytokines did not produce the same toxic effect as the triplecytokine combination. Hence, the period of experimentation was extendedto 10 days and cytokines were used at two times and five times higherthan the concentrations used in FIG. 9.

By day 10 only 15±2% of cytokine treated MIN-6 cells remained viablecompared to 100±1% for untreated cells (P=0.0011) even after theconcentrations were increased by up to 5 times the initialconcentrations (FIGS. 13a and b ). These experiments indicated thatincreasing cytokine concentrations beyond did not further reduce cellviability.

In summary, after titrating the cytokine concentrations on the MIN-6cell line it was determined that the following concentrations would besuitable for future experiments over 10 days because they were mosttoxic to the pancreatic β-cell line when replenished daily IFN-γ (384ng/mL), TNF-α (long/mL) and IL-1β (2000 pg/mL).

MTT Assay

After establishing the optimised cytokine treatment to reduce theviability of MIN-6 cells, these experimental parameters were applied toHuh7 and Huh7ins cells. This was done to determine if the cytokineswould have the same effect on the hepatoma cell lines with and withoutthe insulin gene.

A significant difference in the susceptibility of MIN-6 cells andHuh7ins cells to cytokine-induced toxicity was observed from day 3(P=0.018) (FIGS. 14a and c ). By day 3, MIN-6 and Huh7ins cells thatwere treated with cytokines had viabilities of 72±5%. Untreated MIN-6cells remained exponentially viable (100±1%) over the 10 days of theexperiment. Treatment of MING cells with the triple cytokines for 10days caused a significant decrease in cell viability when compared tountreated cells (P=0.0039) (FIG. 14a ).

When exposed to the cytokine combination for 10 days, Huh7, Huh7ins andMelligen cells showed no significant decrease in cell viability comparedto the untreated control cells of each cell line (FIG. 14 b-d).

Apoptosis and Cell Cycle Arrest are not Induced by Cytokine Cocktail inInsulin-Secreting Human Hepatoma Cells

Translocation of the phosphotidylserine from the inner side of theplasma membrane to its outer layer is an early event of apoptosis.Annexin V is a calcium dependent phospholipid-binding protein with highaffinity for phosphatidylserine. Propidium iodide (PI) is a standardcytometric viability probe that is excluded by cells with intactmembrane. PI staining is performed simultaneously with the annexin Vstaining to differentiate apoptotic cells (single annexin V-positive)from necrotic cells (double annexin V-PI-positive), as necrotic cellsalso expose phosphatidylserine to annexin V because of the loss ofmembrane integrity (Vermes et al., 1995). Student's t-test was used andP values less than 0.05 were considered to be statistically significant.

Analysis of annexin V binding was performed at 24 and 48 h with andwithout cytokine treatment. Staining Melligen cells at 24 h time-pointshowed close to 0% annexin V-single positive cells (apoptotic) and 0%annexin V PI-double positive cells (late apoptotic) and 20% stainingPI-only (necrotic). At 48 h, the percentage of necrotic cells in thecytokine-treated group did not differ significantly from that recordedin the untreated samples (19%).

To elucidate the effect of cytokines on the viability of Huh7ins,Melligen and MIN-6 cells using PI-only staining, the cells wereincubated with the cytokine cocktail for 48 h. The viable cell numberwas not decreased in the insulin-secreting hepatoma cells by thecytokine cocktail treatment at 24 h and 48 h according to the MTT assay(FIG. 14). To examine whether the cytokine cocktail treatment inducedapoptosis or cell-cycle arrest in Huh7ins and Melligen cells, the DNAcontent in these cells were analysed using flow cytometry afterpropidium iodide staining. In both insulin-secreting hepatoma cells, thecytokine treatment did not affect the number of cells in the subG1 phaseof cell-cycle, representing apoptotic cells (FIGS. 17 and 18). Inaddition, there was no increase in the number of cells in the S-phase orG0/G1 phase, suggesting that cytokines do not reduce the viable numberof cells through inducing apoptosis and cell cycle arrest at G0/G1 phasein insulin-secreting hepatoma cells. MIN-6 cell results not shown.

Cell Morphology

In FIGS. 19a, 19b and 19c , the untreated MIN-6 cells appeared to haveintact cell membranes and remained attached to the plate in coloniesgrowing as monolayers. By day 12 MIN-6 cells were confluent. Incontrast, cytokine-treated MIN-6 cells started to degenerate withruptured membranes causing cells to detach after 6 days (FIG. 19e ).Complete degeneration with cell debris scattered between remaining cellswas seen on day 12 (FIG. 19f ).

Co-incubation of Huh7ins and Melligen cells with the cocktail ofpro-inflammatory cytokines did not induce morphological changesconsistent with cell death after day 1 (FIG. 20d ) or day 6 (FIG. 20e ).At both these time-points Huh7ins and Melligen cells were attached andof uniform size. However, by day 10 the cytokine-treated Huh7ins cells(FIG. 20f ) appeared less dense when compared to the untreated cells(FIG. 20c ). The remaining treated cells appeared intact, attached andthere was an absence of cell debris as observed for the cytokine-treatedMIN-6 cells. The morphology of both the MIN-6 and liver cell linescorroborates the results obtained from the MTT cell viability assay,which indicated that liver cell lines were more resistant to the toxiceffects of the pro-inflammatory cytokines.

Cytokine Receptors and Cell Signalling Cascades:

To establish if observed resistance of the liver cell line to thepro-inflammatory cytokine cocktail is due to the absence of the cytokinereceptors, RT-PCR was performed using cDNA generated from RNA isolatedfrom human primary islet (positive control), Huh7 (parent cell line),Huh7ins (Huh7 transfected with the insulin gene) and Melligen (furthermodified Huh7ins) cells with primers for IFNR1, IFNR2, IL1R1, IL1R2,TNFR1 and TNFR2. Molecular expression of cytokine receptors IFNR1,IFNR2, IL1R1, IL1R2 and TNFR1 was confirmed in all cells (FIG. 21).Therefore, the reduced susceptibility to cytokine-induced killingdisplayed by Melligen cells cannot be attributable to the absence ofreceptors for the cytokines.

RT-PCR was performed using primers for IFNR1, IFNR2, IL1R1, IL1R2, TNFR1and TNFR2 cytokine receptors. Lanes contain cDNA for: 1-Pancreatic IsletCells (positive control) 2-Huh7 Cells 3-Huh7ins Cells 4-Melligen Cells5-Negative control. Results show bands for IFNR1, IFNR2, IL1R1, IL1R2and TNFR1 but not TNFR2 cytokine receptor.

Downstream of TNF receptor (TNFR) 1 associated death domain protein(TRADD), receptor-interaction protein and TNF receptor associated factor(TRAF) 2 activate the NF-κB pathway. NF-κB has been reported to initiatethe expression of various genes associated with anti-apoptosis, cellgrowth, and immune response in liver cells. No significant difference inthe cytokine-induced activation of NF-κB was observed between thetreated Huh7, Huh7ins and Melligen cells (FIG. 23). These resultsindicate that the cytokine cocktail induces NF-κB activationirrespective of the presence of the insulin gene, and the anti-apoptoticmechanism in these liver cell lines seems to be independent of NF-κBactivation.

Iκb Gene Expression in Cytokine-Induced Insulin-Secreting Human HepatomaCell

To investigate the downstream effects of inhibiting NFkB signalling,cytokine-induced gene expression in Huh7, Huh7ins and Melligen cells wasevaluated. Gene expression of Fas and iNOS was switched off after theaddition of cytokines to the liver cell lines (FIG. 22). After cytokineexposure, the relative abundance of iNOS and Fas mRNAs (optical densitycorrected per GAPDH abundance) was, respectively about 2-fold lower incontrol cells not treated with the cytokine cocktail expression of thehousekeeping gene GAPDH was not affected by exposure to cytokines.

Nitric Oxide Determination

The iNOS enzymatic activity was estimated by measurements of mediumnitrite (a stable product of nitric oxide (NO) oxidation) accumulationby the modified Griess reaction during a 48 h exposure to cytokines,IFN-γ (384 ng/mL), TNF-α (long/mL) and IL-1β (2000 pg/mL). In themodified Greiss reaction, nitric oxide production by MIN-6, Huh7,Huh7ins and Melligen cells was measured as nitrite accumulation inconditioned medium and determined by the modified Griess reaction. Inbrief, 50 μL of cell free medium were mixed with an equal volume of 1%sulphanilamide (Sigma, USA) in 5% phosphoric acid. The plate wasincubated for 5 to 10 minutes at room temperature, protected from light.NED solution (0.1% N-1-naphthylethylenediamine dihydrochloride in water)(Sigma, USA), 50 μL per well, was then added to all wells and the platewas again incubated for 5-10 minutes at room temperature, protected fromlight. The nitrite concentration was determined in triplicate within aconcentration range that corresponded to the linear part of the standardcurve. Absorbance was measured at 540 nm in a microplate reader (BioTek,USA).

Using the modified Griess reaction amounts of nitrite released into theculture media of cytokine treated and untreated MIN-6 cells weredetermined at 24 h and 48 h. Significantly higher concentrations of NOwere detected in cytokine treated MIN-6 cells at both 24 h and 48 h(P<0.01). Treated Huh7, Huh7ins and Melligen cells on the other hand didnot exhibit an increase in NO production compared to untreated cells ateither 24 h or 48 h time-points (P>0.05). (FIG. 24)

Effect of Cytokines on Insulin Secretion, Storage and GlucoseResponsiveness

For Melligen cells to be suitable candidates as artificial β-cells theymust continue to be glucose-responsive and store and secrete insulin inthe pro-inflammatory cytokine milieu. Therefore, the effects of IFN-γ,TNF-α and IL-1β on insulin secretion, storage and glucose-responsivenessof Huh7ins and Melligen cells were determined.

The glucose-responsive insulin secreting pancreatic β-cell line, MIN-6,(Miyazaki et al., 1990), was used as a positive control. To determine ifthe triple cytokine treatment had an effect on chronic insulinsecretion, storage and glucose responsiveness, the cells were exposed tocytokines [IFN-γ (384 ng/mL), TNF-α (long/mL) and IL-1β (2000 pg/mL)].Media and cytokines were changed daily over the 10-day period studied.An insulin RIA was used to determine insulin concentration in thesamples collected.

Chronic Insulin Secretion and Storage

Cytokine-treated MIN-6 cells secreted significantly less insulin(14005±1317 ng/well) than untreated MIN-6 cells (21408±814 ng/well) atday 1 (P=0.012) and throughout the entire period studied (FIG. 25a ).Insulin levels for cytokine-treated MIN-6 cells at day 10 representedthe total amount of insulin secreted over the entire 10 days. Incontrast, Huh7ins cells co-incubated with cytokines secreted amounts ofinsulin that were not significantly different to those secreted by theuntreated Huh7ins and Melligen cells over the 10-day period (FIG. 25b ).

Effect of Cytokines on Insulin Storage

MIN-6, Huh7ins and Melligen cells were treated over 10 days withcytokine cocktail IFN-γ, TNF-α and IL-1β. Stored insulin was extractedusing acid ethanol method and amounts of insulin determined by RIA ondays 1, 2, 3, 5, 8, and 10. MIN-6 cells were significantly affected bythe cytokine treatment at day 2 (P<0.05) in contrast to this Huh7ins andMelligen cells retained their ability to store insulin over the entire10 days without significant difference between the treated and untreatedcells (P>0.05).

From FIG. 26a it can be seen that insulin storage per well steadilyincreased in untreated MIN-6 cells over the 10 days of the experiment asthe cells proliferated. After exposure of MIN-6 cells to the cytokinemixture over 10 days, insulin content was significantly diminished afterday 1 compared to the control MIN-6 cells (P=0.017). The differencebetween the treated and untreated MIN-6 cells continued to besignificant throughout the remaining days of the experiment. Incontrast, Huh7ins and Melligen cells treated with the cytokinecombination did not show a significant difference in insulin storagecompared to the untreated Huh7ins and Melligen cells respectively.

Glucose Responsiveness

After 10 days of cytokine treatment of MIN-6 cells there was asignificant decrease in insulin response to a glucose stimulus whencompared to the control MIN-6 cells (P=0.0009). Insulin secretion ofuntreated MIN-6 cells in response to 20 mM glucose increased more than5-fold over 1 h when compared to basal levels (692±78 ng/well/h)(P=0.0002) (FIG. 27a ). The treated MIN-6 cells did not releasesignificantly higher levels of insulin to the glucose stimulus comparedto basal levels (P=0.60) (FIG. 27a ). This was because the cellsexhibited reduced viability after 10 days of co-incubation withcytokines, whereas control cells continued in log growth. Therefore, atday 10 there were more control cells and hence greater insulin storage.This data showed that the control cells responded to the 20 mM glucosestimulus, confirming that MIN-6 cells constituted an appropriate β-cellmodel.

The effect of the cytokines on glucose-responsiveness was alsodetermined for the Huh7ins and Melligen cells. Untreated Huh7ins andMelligen cells gave a 5-fold increase in insulin secretion whenstimulated with 20 mM glucose, with return to basal levels of insulinsecretion (0.13±0.014 pmol/well/h) upon removal of the glucose stimulus(FIGS. 27b and c ). Huh7ins and Melligen cells incubated with cytokinesfor 10 days showed a 4.5-fold increase in insulin secretion upon the 20mM glucose stimulus and a return to basal levels of secretion(0.06±0.006 pmol/well/h) within 1 h after stimulation (FIGS. 27b and c). The amount of insulin secreted by the treated Huh7ins and Melligencells during the stimulus was not significantly different to the resultobtained for the untreated Huh7ins and Melligen cells respectively. Thisindicates that Huh7ins and Melligen cells retain the ability to respondto a glucose stimulus even after 10 days of cytokine treatment.

Huh7ins and Melligen cells were cultured for 10 days with and withoutcytokines. At day 10, the cells were stimulated with increasingconcentrations of glucose in basal medium. Huh7ins cells secretedincreased amounts of insulin in response to 2.5 mM glucose and Melligencells at 4.25 mM glucose. In both cell lines there was no significantdifference observed between cytokine treated and untreated cells at anyglucose concentration (P>0.05) (FIG. 28).

Example 5 Analysis of Expression of β-Cell Transcription Factors inMelligen Cells

In this study, the level of pancreatic transdifferentiation that hasoccurred in Huh7ins and Melligen cells was detected. The expression ofselected β-cell transcription factors, pancreatic hormones, andcomponents of the glucose sensing apparatus [(GLUT2 and glucokinase(GK)] of pancreatic cells in the Huh7ins and Melligen cells togetherwith the parent cell line Huh7 was analysed (FIG. 29).

Methods RT-PCR

The RNA obtained from the cell lines was used to reverse transcribecomplimentary DNA (cDNA) by using the reverse transcription reagents(Promega, U.S.A), which were made up to a 404, reaction mixture,containing RT buffer, Random primers, RNase inhibitor, dNTP mixture,Reverse transcriptase, RNase-free dH₂O. The volume for each reagent islisted in Table 2. All reagents were spun down to mix and incubated at37° C. for 1 hour; this was followed by a 99° C. heat shock for 1minute. The tubes were immediately transferred to ice and were ready touse for further amplification.

TABLE 2 CONTENTS OF REVERSE TRANSCRIPTION MIXTURE Reagents Volume (μL) 5× AMP RT Buffer 8 Random Primers (500 μg/mL) 3 RNase Inhibitor (40units/uL reaction) 1 dNTP mixture (10 mM) 4 Reverse Transcriptase (10units) 1.5 Template RNA 3 RNase-free dH₂O 19.5 Total Volume 40

The possibility of cDNA contamination in total isolated RNA wasexcluded, due to the addition of 1.5 μL of DNase (1 unit/μL) to 60 μL ofmRNA preparation. The sample was also examined following electrophoresisin a 1.5% agarose gel.

Specific final primer sequences are listed in Table 3, including: PDX1,NEUROG3, NEUROD1, NKX2-2, NKX6-1, PAX6, PC1/3, PC2, liver GK, islet GK,GLUT2, glucagon, somatostatin (SST), and pancreatic polypeptide (PP).These primers were diluted to 1 μg/μL, and further diluted 1:8 for PCRreactions.

TABLE 3 LIST OF GENE-SPECIFIC PRIMERS: THE SEQUENCES, THE SIZES OFPRODUCTS, AND ANNEALING TEMPERATURE. Annealing Gene Forward Reversetemp.(° C.) References PDX-1 * 5′CCCATGGATGAAGT 5′GTCCTCCTCCTTTTT 60Street et al., (262 bp) CTACC3′ CCAC3′ 2004 (SEQ ID NO: 6)(SEQ ID NO: 7) Ngn3 51AGACGACGCGAAGC 51AAGCCAGACTGCCT 69 Heremans et(286 bp) TCACC3′ GGGCT3′ al., 2002 (SEQ ID NO: 8) (SEQ ID NO: 9) NeuroD5′TCACTGCTCAGGAC 5′CTCCTCGTCCTGAGA 53 Westemman (139 bp) CTACTAA3′ACTG3′ et al., 2004 (SEQ ID NO: 10) (SEQ ID NO: 11) Nkx2.25′TGCAGCACATGCAGT 5′TCCCAAGGTTCAGAA 56 Heremans et (329 bp) ACAACG3′GGAGAGG3′ al., 2002 (SEQ ID NO: 12) (SEQ ID NO: 13) Nkx6.15′TCTTCTGGCCCGGGG 5′AGCCGCGTGCTTCTT 58 Heremans et (284 bp) TGATG3′CCTCC3′ al., 2002 (SEQ ID NO: 14) (SEQ ID NO: 15) Pax6 5′CAAAAGTCCAAGTG5′CCCATCTGTTGCTTT 56.1 Heremans et (301 bp) CTGGACAA3′ TCGCT3′ al., 2002(SEQ ID NO: 16) (SEQ ID NO: 17) PC 1/3 5′CTCCTAAAAGACTT 5′TCCACACAGGCACT51.9 Zalzman et al., (404 bp) GCGGAATCAC3′ AAGAAAGACTG3′ 2005(SEQ ID NO: 18) (SEQ ID NO: 19) PC 2 5′GCGGGATTACCAGT 5′TGTGCTTTCAGAGAT55.3 Zalzman et al., (572bp) CCAAGTTG3′ GTGGCG3′ 2005 (SEQ ID NO: 20)(SEQ ID NO: 21) GLUT2 5′TTGGTGTGATCAATG 5′GCCACAGTCTCTTCC 56 Designed(180 bp) CACCT3′ TCAGC3′ (SEQ ID NO: 22) (SEQ ID NO: 23) Liver GK5′CTGCCTCCCAAAGC 5′GATCTTGGTCTGGGC 58 Designed (186 bp) ATCTAC3′ ATGTT3′(SEQ ID NO: 24) (SEQ ID NO: 25) Islet GK 5′TCAGAAGCCTACTG5′CTTCTGCATCCGTCT 68 Designed (176 bp) GGGAAG3′ CATCA3′ (SEQ ID NO: 26)(SEQ ID NO: 27) Glucagon 5′CCCAAGATTTTGTGC 5′GCGGCCAAGTTCTTC 56Heremans et (221 bp) AGTGGTT3′ AACAAT3′ al., 2002 (SEQ ID NO: 28)(SEQ ID NO: 29) Somatostatin S'ATGCTGTCCTGCCGC S'ACAGGATGTGAAAG 61Monges et al., (348 bp) CTCCAG3′ TCTTCCA3′ 1996 (SEQ ID NO: 30)(SEQ ID NO: 31) Pancreatic 5′CAATGCCACACCAG 5′TGGGAGCAGGGAGC 60Zalzman et al., polypeptide AGCAGATG3′ AAGC3′ 2005 (267 bp)(SEQ ID NO: 32) (SEQ ID NO: 33)Real time PCR

Real-time PCR was performed to determine the level of expression of somefactors that were detected by RT-PCR in different cell lines, and toevaluate the effect of the overexpression of human islet GK in Melligencells (FIG. 30).

Quantitative real time PCR was performed by using a Prism 7500 (ABI).Platinum SYBR Green qPCR supermix-UDG kit (Invitrogen) was used asamplification reagents. The primers are listed in Table 3.

Amplification conditions included initiation 50° C. for 2 min anddenatured at 96° C. for 10 min, followed by 40 cycles and each cycleincluded denaturation at 96° C. 35 seconds, annealing at 58° C. (forhuman islet glucokinase cDNA) or 66.5° C. (for liver glucokinase gene)35 seconds and extension at 72° C. 35 seconds.

Relative quantitative analysis was performed according to thecomparative C_(T) value by using the arithmetic formula 2⁻(ΔΔCt). ThecDNA levels were normalized to house keeping gene (human GAPDH).

Western Blot

Western analysis was performed for PDX1 as previously described in Huh7,Huh7ins and Melligen cells using human PDX1 (rabbit anti human, 1:1000dilution, Chemicon) and secondary antibody to rabbit (Upstate, USA).

Results Human Islet and Liver Glucokinase Genes in Different Cell Types.Level of Expression of Liver Glucokinase in Melligen and Huh7ins Cells

As liver GK has found to be endogenously expressed in all theliver-derived cell lines by RT-PCR, the difference in the level ofexpression was further determined by real-time PCR among the cell lines.There was a significantly (p<0.0001) higher expression in Melligen cellscompared to the Huh7ins cells with empty vector (no islet GK) (FIG. 31a). No significant difference (p=0.268) in the expression of liver GK wasseen in the Huh7ins cells with empty vector (carry no islet GK) comparedto the Huh7ins cells (FIG. 31b ). Relative quantitative analysisperformed according to the comparative C_(T) value by using thearithmetic formula 2⁻(ΔΔCt), showed that Melligen cells liverglucokinase expression was 5.133-fold higher expression than that ofHuh7ins cells with vector only.

Level of Expression for β-Cell Transcription Factor, PDX1

While the expression of PDX-1 at the mRNA level was shown in the Huh7,Huh7ins, and Melligen cells by RT-PCR, real-time PCR analysis wasperformed to determine if any difference in the level of expressionoccurred among the cell lines. The paired t-test showed there was asignificant difference (p<0.0001) in expression of PDX-1 in Melligencells when compared to Huh7ins cells, Melligen cells had 2.908-foldhigher expression than the Huh7ins cells according to the C_(T) value(FIG. 32).

Real-time PCR analysis indicated there was no significant difference inthe expression of NEUROD, seen between Melligen cells and Huh7ins cells(FIG. 33).

Level of Expression for the Glucose Transporter, GLUT2

To determine whether overexpression of human insulin and human islet GKrespectively in the Huh7ins and Melligen cells had any effect on GLUT2expression at the mRNA level, real-time PCR experiments were performedon the cDNAs obtained from the Huh7, Huh7ins, and Melligen cells. FIG.34 demonstrates that the level of expression for GLUT2 in Melligen cellswas significantly (p<0.0001) higher compared to Huh7 and Huh7ins cells.There was no significant difference (p=0.013) in expression of GLUT2between Huh7 and Huh7ins cells.

Western Analysis

The specific PDX-1 protein was revealed by western blotting analysis inHuh7, Huh7ins, and Melligen cells was detected at 35 kDa (FIG. 35).

Those skilled in the art will appreciate that the invention describedherein is susceptible to variations and modifications other than thosespecifically described. It is to be understood that the inventionincludes all such variations and modifications. The invention alsoincludes all of the steps, features, compositions and compounds referredto or indicated in this specification, individually or collectively, andany and all combinations of any two or more of said steps or features.

BIBLIOGRAPHY

-   Auricchio, A. et al., 2002, Constitutive and regulated expression of    processed insulin following in vivo hepatic gene transfer, Gene    Therapy 9: 963-71.-   Bartlett, R. J. et al., 1998, Toward engineering skeletal muscle to    release peptide hormone from the human pre-proinsulin gene,    Transplant Proc. 30(2):451.-   Beckman, J. A., Creager, M. A., and Libby, P. 2002. Diabetes and    atherosclerosis: epidemiology, pathophysiology, and management. JAMA    287:2570-2581.-   Ber, I. et al., 2003, Functional, persistent, and extended liver to    pancreas transdifferentiation. Journal of Biological Chemistry 278:    31950-31957.-   Bochan, M. R. et al., 1998, Stable transduction of human pancreatic    adenocarcinoma cells, rat fibroblasts, and bone marrow-derived stem    cells with recombinant adeno-associated virus containing the rat    preproinsulin II gene, Transplant Proc. 30(2):453-4.-   Cardozo, A. K. et al., 2001, A comprehensive analysis of    cytokine-induced and nuclear factor-kappa B-dependent genes in    primary rat pancreatic beta-cells, J Biol Chem. 276(52):48879-86.-   Cheung, A. T. et al., 2000, Glucose-dependent insulin release from    genetically engineered K cells, Science 290(5498):1959-62.-   de la Luna, S., et al., 1988, Gene 62:121-128.-   Efrat S., 2004, Regulation of insulin secretion: insights from    engineered beta-cell lines, Ann N Y Acad Sci. 1014:88-96. Review.-   Falqui, L. et al., 1999, Reversal of diabetes in mice by    implantation of human fibroblasts genetically engineered to release    mature human insulin, Human Gene Therapy 10 (11):1741-1742.-   Falqui, L. et al., 1999, Reversal of diabetes in mice by    implantation of human fibroblasts genetically engineered to release    mature human insulin, Hum Gene Ther. 10(11):1753-62.-   Ferber, S. et al., 2000, Pancreatic and duodenal homeobox gene 1    induces expression of insulin genes in liver and ameliorates    streptozotocin-induced hyperglycaemia, Natural Medicine    6(5):568-572.-   Hathout, E. et al., 2003, Islet transplant: an option for childhood    diabetes?, Arch Dis Child. 88(7):591-4. Review.-   Heremans, Y. et al., 2002, Recapitulation of embryonic    neuroendocrine differentiation in adult human pancreatic duct cells    expression neurogenin 3, The Journal of Cell Biology 159(2):303-311.-   Huang, M. T. F. and Gorman, C. M., 1990, Nucleic Acids Res.    18:937-947-   Hughes, S. D. et al., 1992, Engineering of glucose-stimulated    insulin secretion and biosynthesis in non-islet cells, Proc Natl    Acad Sci USA. 89(2):688-92.-   Imai, J. et al., 2004, Constitutively active PDX1 induced efficient    insulin production in adult murine liver, Biochemical and    Biophysical Research Communications 326:402-409.-   Jackson, R. J. et al., 1990, Trends Biochem. Sci. 15:477-483-   Janeesens and Tschopp, 2006, Signals from within: the    DNA-damage-induced NF-κB response, Cell Death and Differentiation,    Review, 13: 773-784.-   Jang, S. K. et al., 1988, J. Virol. 62:2636-2643-   Karasik, A. et al., 2005, Cell-replacement therapy for diabetes:    Generating functional insulin-producing tissue from adult human    liver cells, PNAS 102 (22):7964-7969.-   Kasten-Jolly, J. et al., 1997, Reversal of hyperglycaemia in    diabetic NOD mice by human proinsulin gene therapy, Transplantation    Proceedings 29: 2216-2218.-   Kim and Park, 2001, Modulated insulin delivery from    glucose-sensitive hydrogel dosage forms, J Control Release    77(1-2):39-47.-   Kojima, H. et al., 2003, NeuroD-betacellulin gene therapy induces    islet neogenesis in the liver and reverse diabetes in mice, Nature    Medicine 9(5): 596-603.-   Kolodka, T. M. et al., 1995, Gene therapy for diabetes mellitus in    rats by hepatic expression of insulin, Proceedings of the National    Academy of Sciences of the United States of America 92: 3293-3297.-   Kutlu, B. et al., 2003, Molecular regulation of monocyte    chemoattractant protein-1 expression in pancreatic beta-cells,    Diabetes 52(2):348-55.-   Kuwajima, M. et al. 1996. The glucose phosphorylating capacity of    liver as measured by three independent assays: implication for the    mechanism of hepatic glycogen synthesis. J Biol. Chem. 261: 8849-53.-   Levine and Leibowitz, 1999, Towards gene therapy of diabetes    mellitus, Mol Med Today 5(4):165-71. Review.-   Lipes, M. A. et al., 1996, Insulin-secreting non-islet cells are    resistant to autoimmune destruction, Proc Natl Acad Sci USA.    93(16):8595-600.-   Mandrup-Poulsen T., 2001, beta-cell apoptosis: stimuli and    signalling, Diabetes 50 Suppl 1:S58-63. Review.-   McAlister, V. C. et al., 2000, Sirolimus-tacrolimus combination    immunosuppression, Lancet. 355:376-377.-   Monges, G. et al., 1996, Gastrointestinal hormone mRNA expression in    human colonic adenocarcinomas, hepatic metastases and cell lines, J    Clin Pathol: Mol Pathol. 49:Mi 59-Mi65.-   Nakayama, M. et al., 2005, Prime role for an insulin epitope in the    development of type 1 diabetes in NOD mice, Nature 435(7039):220-3.-   Ortis, F. et al., 2006, Cytokine-induced proapoptotic gene    expression in insulin-producing cells is related to rapid,    sustained, and nonoscillatory nuclear factor-kappaB activation, Mol    Endocrinol. 20(8): 1867-79.-   Permutt, M A et al., 1989, Cloning and functional expression of a    human pancreatic islet glucose-transporter, Proc Natl Acad Sci USA,    86:8688-8692-   Pinkse, G. G. et al., 2005, Autoreactive CD8 T cells associated with    beta cell destruction in type 1 diabetes, Proc Natl Acad Sci USA.    102(51):18425-30.-   Rees, S. et al., 1996, BioTechniques 20:102-104-   Sapir, T. et al., 2005, Cell-replacement therapy for diabetes:    Generating functional insulin-producing tissue from adult human    liver cells. PNAS 102 (22):7964-7969.-   Seewaldt, S. et al., 2000, Virus-induced autoimmune diabetes: most    beta-cells die through inflammatory cytokines and not perforin from    autoreactive (anti-viral) cytotoxic T-lymphocytes, Diabetes    49(11):1801-9.-   Selden, R. F. et al., 1987, Regulation of insulin-gene expression.    Implication for gene therapy, The New England Journal of Medicine    317 (17):1067-1076.-   Simpson, A. M. et al., 1993, Transformation of pituitary and    fibroblast cell lines using human insulin cDNA and a    dexamethasone-inducible promoter, Transplantation Proceedings    25:2915-2916.-   Tabiin, M. T. et al., 2001, Susceptibility of insulin-secreting    hepatocytes to the toxicity of pro-inflammatory cytokines, J    Autoimmun. 17(3):229-42.-   Taniguchi, H. et al., 1997, Constant delivery of proinsulin by    encapsulation of transfected cells, J Surg Res. 70(1):41-5.-   Truong, W. et al., 2005, Clinical islet transplantation at the    University of Alberta—the Edmonton experience, Clin Transpl. 153-72.-   Tuch, B. E. et al., 2003, Function of a genetically modified human    liver cell line that stores, processes and secretes insulin, Gene    Ther. 10(6):490-503.-   Verge, C. F. et al., 1996, Prediction of type I diabetes in    first-degree relatives using a combination of insulin, GAD, and    ICA512bdc/IA-2 autoantibodies, Diabetes 45(7):926-33.-   Vermes, I. et al., 1995, A novel assay for apoptosis. Flow    cytometric detection of phosphatidylserine expression on early    apoptotic cells using fluorescein labelled Annexin V, J Immunol    Methods 184(1):39-51.-   Vollenweider, F. et al., 1992, Processing of proinsulin by    transfected hapatoma (FAO) cells, Journal of Biological Chemistry    267:14629-14623.-   Westerman, B. A. et al., 2004, NEUROD1 acts in vitro as an upstream    regulator of NEUROD2 in trophoblast cells, Biochimica et Biophysica    Acta 1676: 96-103.-   Wilson, J. E. 1984. Regulation of mammalian hexokinase activity. In:    Regulation of carbohydrate metabolism. Beitner R ed. Boca Raton,    Fla., CRC Press. P. 45-85.-   Wong, R. Y. L. et al., 1999, Expression of human insulin in    haematopoietic mononuclear cells: potential gene therapy for type I    diabetes, 7^(th) World Congress of the International Pancreas and    Islet Transplant Association, Sydney 7: 122.-   Zalzman, M. et al., 2003, Reversal of hyperglycemia in mice by using    human expandable insulin-producing cells differentiated from fetal    liver progenitor cells, PNAS 100(12):7253-7258.

1. (canceled)
 2. A method of modulating glucose levels in a mammal saidmethod comprising administering to said mammal an effective number ofisolated genetically modified hepatocytes recombinantly expressinginsulin protein, human pancreatic islet glucokinase protein, and GLUT2protein, and wherein the isolated genetically modified hepatocytesintracellularly store insulin and commence secretion of said insulinwhen exposed to an extracellular glucose concentration ranging in anamount from about 3 mM to about 8 mM.
 3. The method of claim 2, whereinthe insulin protein is a human insulin protein, and the GLUT2 protein isa human GLUT2 protein.
 4. The method of claim 2, wherein the humanpancreatic islet glucokinase protein has an amino acid sequence of SEQID NO: 2 or a sequence that is at least 90% identical to SEQ ID NO: 2.5. The method of claim 2, wherein the isolated genetically modifiedhepatocytes are human hepatocytes.
 6. The method of claim 2, wherein theisolated genetically modified hepatocytes are Huh7 cells.
 7. The methodof claim 2, the isolated genetically modified hepatocytes are autologouscells, allogenic cells, or combination thereof.
 8. The method of claim2, isolated genetically modified hepatocytes are encapsulated.
 9. Themethod of claim 2, wherein the mammal is a human.
 10. The method ofclaim 2, wherein the mammal is diagnosed with diabetes.
 11. The methodof claim 10, wherein the diabetes is type 1 diabetes, IDDM, gestationaldiabetes, slowly progressive IDDM, latent autoimmune diabetes, type 2diabetes, or combinations thereof.
 12. The method of claim 2, whereinthe administration comprises injection or transplantation.